# Project Euler 403
# S(10^12) mod 10^8. All polys evaluated mod 24*(2*10^8) then /24.
import euler.nt { isqrt }
function modmul(a: i64, b: i64, mod: i64) -> i64 {
let r: i128 = (a as i128) * (b as i128) % (mod as i128)
if r < (0 as i128) { return (r + (mod as i128)) as i64 }
return r as i64
}
function modadd(a: i64, b: i64, mod: i64) -> i64 {
let mut s: i64 = a + b
s = s % mod
if s < 0 { s = s + mod }
return s
}
function g_mod(n: i64, m2: i64) -> i64 {
# g(n)=(n^3+5n+6)/6 ; work mod 6*m2
let mod: i64 = 6 * m2
let n1: i64 = n % mod
if n1 < 0 { n1 = n1 + mod }
let n2: i64 = modmul(n1, n1, mod)
let n3: i64 = modmul(n2, n1, mod)
let num: i64 = modadd(modadd(n3, modmul(5, n1, mod), mod), 6, mod)
return num / 6
}
function G_mod(n: i64, m2: i64) -> i64 {
if n < 0 { return 0 }
let mod: i64 = 24 * m2
let n1: i64 = n % mod
let n2: i64 = modmul(n1, n1, mod)
let n3: i64 = modmul(n2, n1, mod)
let n4: i64 = modmul(n2, n2, mod)
let mut num: i64 = n4
num = modadd(num, modmul(2, n3, mod), mod)
num = modadd(num, modmul(11, n2, mod), mod)
num = modadd(num, modmul(34, n1, mod), mod)
num = modadd(num, 24, mod)
return num / 24
}
function H_mod(n: i64, m2: i64) -> i64 {
if n < 0 { return 0 }
let mod: i64 = 24 * m2
let n1: i64 = n % mod
# s1 = n(n+1)/2
let s1_num: i64 = modmul(n1, n1 + 1, 2 * mod)
# use exact division carefully via mod 2*mod then /2 - ensure even
let s1: i64 = (s1_num % (2 * mod)) / 2
s1 = s1 % mod
# s2 = n(n+1)(2n+1)/6
let t2: i64 = modmul(modmul(n1, n1 + 1, 6 * mod), (2 * n1 + 1) % (6 * mod), 6 * mod)
let s2: i64 = t2 / 6
s2 = s2 % mod
let s3: i64 = modmul(s1, s1, mod)
# s4 = n(n+1)(2n+1)(3n^2+3n-1)/30
let u: i64 = modmul(n1, n1 + 1, 30 * mod)
u = modmul(u, (2 * n1 + 1) % (30 * mod), 30 * mod)
let v: i64 = (modmul(3, modmul(n1, n1, 30 * mod), 30 * mod) + modmul(3, n1, 30 * mod) - 1) % (30 * mod)
if v < 0 { v = v + 30 * mod }
let t4: i64 = modmul(u, v, 30 * mod)
let s4: i64 = t4 / 30
s4 = s4 % mod
let mut num: i64 = s4
num = modadd(num, modmul(2, s3, mod), mod)
num = modadd(num, modmul(11, s2, mod), mod)
num = modadd(num, modmul(34, s1, mod), mod)
num = modadd(num, modmul(24, n1 + 1, mod), mod)
return num / 24
}
function sum_G_mod(l: i64, r: i64, m2: i64) -> i64 {
if l > r { return 0 }
let mut v: i64 = H_mod(r, m2) - H_mod(l - 1, m2)
v = v % m2
if v < 0 { v = v + m2 }
return v
}
function min64(a: i64, b: i64) -> i64 {
if a < b { return a }
return b
}
function main() -> i32 {
let MOD: i64 = 100000000
let M2: i64 = 2 * MOD
let N: i64 = 1000000000000
let s: i64 = isqrt(N)
let mut total: i64 = (2 * G_mod(N, M2) - 1) % M2
if total < 0 { total = total + M2 }
if N >= 1 {
let f1: i64 = (G_mod(N + 1, M2) + G_mod(N - 2, M2) - 1) % M2
if f1 < 0 { f1 = f1 + M2 }
total = (total + 2 * f1) % M2
}
if N >= 2 {
let fn: i64 = (g_mod(N, M2) + g_mod(N + 1, M2)) % M2
total = (total + 2 * fn) % M2
}
let hi: i64 = min64(s, N - 1)
if hi >= 2 {
let mut small_sum: i64 = 0
let mut p: i64 = 2
while p <= hi {
let m: i64 = N / p
let term: i64 = (G_mod(m + p, M2) + G_mod(m - p, M2) - 1) % M2
if term < 0 { term = term + M2 }
small_sum = (small_sum + term) % M2
p = p + 1
}
total = (total + 2 * small_sum) % M2
}
let mut large_sum: i64 = 0
let mut m: i64 = 1
while m <= s {
let mut l: i64 = N / (m + 1) + 1
let r: i64 = N / m
if r > s {
if l <= s { l = s + 1 }
if l <= r {
let mut term: i64 = 0
if r == N && N >= l {
if l <= N - 1 {
term = (sum_G_mod(l + m, N - 1 + m, M2) - sum_G_mod(l - m - 1, N - 1 - m - 1, M2)) % M2
}
} else {
term = (sum_G_mod(l + m, r + m, M2) - sum_G_mod(l - m - 1, r - m - 1, M2)) % M2
}
if term < 0 { term = term + M2 }
large_sum = (large_sum + term) % M2
}
}
m = m + 1
}
total = (total + 2 * large_sum) % M2
let diag: i64 = 2 * min64(N / 2, isqrt(N)) + 1
total = (total + diag % M2) % M2
let ans: i64 = (total / 2) % MOD
printf("%lld\n", ans)
return 0
}
Generated C
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Flow runtime helpers */
typedef struct flow_temp_node { struct flow_temp_node* next; } flow_temp_node;
static flow_temp_node* flow_temp_head = NULL;
static int flow_temp_atexit_set = 0;
__attribute__((unused)) static void flow_temp_free_all(void) {
while (flow_temp_head) {
flow_temp_node* n = flow_temp_head;
flow_temp_head = n->next;
free(n);
}
}
__attribute__((unused)) static void* flow_temp_alloc(size_t nbytes) {
flow_temp_node* node = (flow_temp_node*)malloc(sizeof(flow_temp_node) + nbytes);
if (!node) return NULL;
node->next = flow_temp_head;
flow_temp_head = node;
if (!flow_temp_atexit_set) {
flow_temp_atexit_set = 1;
atexit(flow_temp_free_all);
}
return (void*)(node + 1);
}
#ifndef FLOW_DIAG
#define FLOW_DIAG(msg) fprintf(stderr, "%s", (msg))
#endif
#ifndef FLOW_LOG
#define FLOW_LOG(fmt, ...) printf(fmt, __VA_ARGS__)
#endif
#ifndef FLOW_LOG_EMPTY
#define FLOW_LOG_EMPTY(fmt) printf(fmt)
#endif
static char* flow_strcat(const char* a, const char* b) {
size_t la = strlen(a ? a : ""), lb = strlen(b ? b : "");
char* r = (char*)flow_temp_alloc(la + lb + 1);
if (!r) return NULL;
if (la) memcpy(r, a, la);
if (lb) memcpy(r + la, b, lb);
r[la + lb] = '\0';
return r;
}
#define __flow_in_arr(arr, val) __extension__ ({ \
int _found = 0; \
size_t _n = sizeof(arr)/sizeof((arr)[0]); \
for (size_t _i = 0; _i < _n; _i++) { \
if ((arr)[_i] == (val)) { _found = 1; break; } \
} _found; })
/* Unified fault handler (MISRA #279) — override with -DFLOW_FAULT_HANDLER=fn */
#ifndef FLOW_FAULT_HANDLER
__attribute__((unused)) static inline void flow_fault_handler(const char* msg) {
fprintf(stderr, "flow: %s\n", msg ? msg : "fault");
abort();
#if defined(__GNUC__) || defined(__clang__)
__builtin_unreachable();
#endif
}
#else
#define flow_fault_handler FLOW_FAULT_HANDLER
#endif
#define flow_div_by_zero_handler() flow_fault_handler("division by zero")
#define flow_shift_ub_handler() flow_fault_handler("invalid shift (amount out of range or left-shift of negative)")
#ifndef FLOW_CHECKED_DIV
#define FLOW_CHECKED_DIV(L, R) (((R) != 0) ? ((L) / (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_MOD
#define FLOW_CHECKED_MOD(L, R) (((R) != 0) ? ((L) % (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHL
#define FLOW_CHECKED_SHL(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull)) && ((L) >= 0)) ? ((L) << (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHR
#define FLOW_CHECKED_SHR(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull))) ? ((L) >> (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#include <math.h>
void* _ui_state = NULL;
static inline float i32_to_f32(int32_t v) { return (float)v; }
/* Host stub for @gpu kernels (device codegen replaces this). */
static inline int32_t gpu_thread_id(void) { return 0; }
int64_t gcd_i64_i64(int64_t a0, int64_t b0);
int64_t lcm_i64_i64(int64_t a, int64_t b);
int64_t isqrt_i64(int64_t n);
int64_t mulmod_i64_i64_i64(int64_t a0, int64_t b0, int64_t mod);
int64_t mod_pow_i64_i64_i64(int64_t base, int64_t exp, int64_t mod);
bool is_prime_i64(int64_t n);
int64_t modmul_i64_i64_i64(int64_t a, int64_t b, int64_t mod);
int64_t modadd_i64_i64_i64(int64_t a, int64_t b, int64_t mod);
int64_t g_mod_i64_i64(int64_t n, int64_t m2);
int64_t G_mod_i64_i64(int64_t n, int64_t m2);
int64_t H_mod_i64_i64(int64_t n, int64_t m2);
int64_t sum_G_mod_i64_i64_i64(int64_t l, int64_t r, int64_t m2);
int64_t min64_i64_i64(int64_t a, int64_t b);
int32_t main(void);
int64_t gcd_i64_i64(int64_t a0, int64_t b0) {
int64_t a = a0;
int64_t b = b0;
while (b != 0) {
int64_t t = FLOW_CHECKED_MOD((a), (b));
a = b;
b = t;
}
return a;
}
int64_t lcm_i64_i64(int64_t a, int64_t b) {
if ((a == 0 || b == 0)) {
return 0;
}
return (FLOW_CHECKED_DIV((a), (gcd_i64_i64(a, b))) * b);
}
int64_t isqrt_i64(int64_t n) {
if (n < 2) {
return n;
}
int64_t x = n;
int64_t y = FLOW_CHECKED_DIV(((x + 1)), (2));
while (y < x) {
x = y;
y = FLOW_CHECKED_DIV(((x + FLOW_CHECKED_DIV((n), (x)))), (2));
}
return x;
}
int64_t mulmod_i64_i64_i64(int64_t a0, int64_t b0, int64_t mod) {
int64_t a = FLOW_CHECKED_MOD((a0), (mod));
int64_t b = FLOW_CHECKED_MOD((b0), (mod));
int64_t result = 0;
while (b > 0) {
if (FLOW_CHECKED_MOD((b), (2)) == 1) {
result = FLOW_CHECKED_MOD(((result + a)), (mod));
}
a = FLOW_CHECKED_MOD(((a * 2)), (mod));
b = FLOW_CHECKED_DIV((b), (2));
}
return result;
}
int64_t mod_pow_i64_i64_i64(int64_t base, int64_t exp, int64_t mod) {
if (mod == 1) {
return 0;
}
int64_t result = 1;
int64_t b = FLOW_CHECKED_MOD((base), (mod));
int64_t e = exp;
while (e > 0) {
if (FLOW_CHECKED_MOD((e), (2)) == 1) {
result = mulmod_i64_i64_i64(result, b, mod);
}
b = mulmod_i64_i64_i64(b, b, mod);
e = FLOW_CHECKED_DIV((e), (2));
}
return result;
}
bool is_prime_i64(int64_t n) {
if (n < 2) {
return 0;
}
if (n < 4) {
return 1;
}
if ((FLOW_CHECKED_MOD((n), (2)) == 0 || FLOW_CHECKED_MOD((n), (3)) == 0)) {
return 0;
}
int64_t i = 5;
while ((i * i) <= n) {
if ((FLOW_CHECKED_MOD((n), (i)) == 0 || FLOW_CHECKED_MOD((n), ((i + 2))) == 0)) {
return 0;
}
i = (i + 6);
}
return 1;
}
int64_t modmul_i64_i64_i64(int64_t a, int64_t b, int64_t mod) {
__int128 r = FLOW_CHECKED_MOD(((((__int128)(a)) * ((__int128)(b)))), (((__int128)(mod))));
if (r < ((__int128)(0))) {
return ((int64_t)((r + ((__int128)(mod)))));
}
return ((int64_t)(r));
}
int64_t modadd_i64_i64_i64(int64_t a, int64_t b, int64_t mod) {
int64_t s = (a + b);
s = FLOW_CHECKED_MOD((s), (mod));
if (s < 0) {
s = (s + mod);
}
return s;
}
int64_t g_mod_i64_i64(int64_t n, int64_t m2) {
int64_t mod = (6 * m2);
int64_t n1 = FLOW_CHECKED_MOD((n), (mod));
if (n1 < 0) {
n1 = (n1 + mod);
}
int64_t n2 = modmul_i64_i64_i64(n1, n1, mod);
int64_t n3 = modmul_i64_i64_i64(n2, n1, mod);
int64_t num = modadd_i64_i64_i64(modadd_i64_i64_i64(n3, modmul_i64_i64_i64(5, n1, mod), mod), 6, mod);
return FLOW_CHECKED_DIV((num), (6));
}
int64_t G_mod_i64_i64(int64_t n, int64_t m2) {
if (n < 0) {
return 0;
}
int64_t mod = (24 * m2);
int64_t n1 = FLOW_CHECKED_MOD((n), (mod));
int64_t n2 = modmul_i64_i64_i64(n1, n1, mod);
int64_t n3 = modmul_i64_i64_i64(n2, n1, mod);
int64_t n4 = modmul_i64_i64_i64(n2, n2, mod);
int64_t num = n4;
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(2, n3, mod), mod);
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(11, n2, mod), mod);
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(34, n1, mod), mod);
num = modadd_i64_i64_i64(num, 24, mod);
return FLOW_CHECKED_DIV((num), (24));
}
int64_t H_mod_i64_i64(int64_t n, int64_t m2) {
if (n < 0) {
return 0;
}
int64_t mod = (24 * m2);
int64_t n1 = FLOW_CHECKED_MOD((n), (mod));
int64_t s1_num = modmul_i64_i64_i64(n1, (n1 + 1), (2 * mod));
int64_t s1 = FLOW_CHECKED_DIV((FLOW_CHECKED_MOD((s1_num), ((2 * mod)))), (2));
s1 = FLOW_CHECKED_MOD((s1), (mod));
int64_t t2 = modmul_i64_i64_i64(modmul_i64_i64_i64(n1, (n1 + 1), (6 * mod)), FLOW_CHECKED_MOD((((2 * n1) + 1)), ((6 * mod))), (6 * mod));
int64_t s2 = FLOW_CHECKED_DIV((t2), (6));
s2 = FLOW_CHECKED_MOD((s2), (mod));
int64_t s3 = modmul_i64_i64_i64(s1, s1, mod);
int64_t u = modmul_i64_i64_i64(n1, (n1 + 1), (30 * mod));
u = modmul_i64_i64_i64(u, FLOW_CHECKED_MOD((((2 * n1) + 1)), ((30 * mod))), (30 * mod));
int64_t v = FLOW_CHECKED_MOD((((modmul_i64_i64_i64(3, modmul_i64_i64_i64(n1, n1, (30 * mod)), (30 * mod)) + modmul_i64_i64_i64(3, n1, (30 * mod))) - 1)), ((30 * mod)));
if (v < 0) {
v = (v + (30 * mod));
}
int64_t t4 = modmul_i64_i64_i64(u, v, (30 * mod));
int64_t s4 = FLOW_CHECKED_DIV((t4), (30));
s4 = FLOW_CHECKED_MOD((s4), (mod));
int64_t num = s4;
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(2, s3, mod), mod);
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(11, s2, mod), mod);
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(34, s1, mod), mod);
num = modadd_i64_i64_i64(num, modmul_i64_i64_i64(24, (n1 + 1), mod), mod);
return FLOW_CHECKED_DIV((num), (24));
}
int64_t sum_G_mod_i64_i64_i64(int64_t l, int64_t r, int64_t m2) {
if (l > r) {
return 0;
}
int64_t v = (H_mod_i64_i64(r, m2) - H_mod_i64_i64((l - 1), m2));
v = FLOW_CHECKED_MOD((v), (m2));
if (v < 0) {
v = (v + m2);
}
return v;
}
int64_t min64_i64_i64(int64_t a, int64_t b) {
if (a < b) {
return a;
}
return b;
}
int32_t main(void) {
int64_t MOD = 100000000;
int64_t M2 = (2 * MOD);
int64_t N = 1000000000000;
int64_t s = isqrt_i64(N);
int64_t total = FLOW_CHECKED_MOD((((2 * G_mod_i64_i64(N, M2)) - 1)), (M2));
if (total < 0) {
total = (total + M2);
}
if (N >= 1) {
int64_t f1 = FLOW_CHECKED_MOD((((G_mod_i64_i64((N + 1), M2) + G_mod_i64_i64((N - 2), M2)) - 1)), (M2));
if (f1 < 0) {
f1 = (f1 + M2);
}
total = FLOW_CHECKED_MOD(((total + (2 * f1))), (M2));
}
if (N >= 2) {
int64_t fn = FLOW_CHECKED_MOD(((g_mod_i64_i64(N, M2) + g_mod_i64_i64((N + 1), M2))), (M2));
total = FLOW_CHECKED_MOD(((total + (2 * fn))), (M2));
}
int64_t hi = min64_i64_i64(s, (N - 1));
if (hi >= 2) {
int64_t small_sum = 0;
int64_t p = 2;
while (p <= hi) {
int64_t m = FLOW_CHECKED_DIV((N), (p));
int64_t term = FLOW_CHECKED_MOD((((G_mod_i64_i64((m + p), M2) + G_mod_i64_i64((m - p), M2)) - 1)), (M2));
if (term < 0) {
term = (term + M2);
}
small_sum = FLOW_CHECKED_MOD(((small_sum + term)), (M2));
p = (p + 1);
}
total = FLOW_CHECKED_MOD(((total + (2 * small_sum))), (M2));
}
int64_t large_sum = 0;
int64_t m = 1;
while (m <= s) {
int64_t l = (FLOW_CHECKED_DIV((N), ((m + 1))) + 1);
int64_t r = FLOW_CHECKED_DIV((N), (m));
if (r > s) {
if (l <= s) {
l = (s + 1);
}
if (l <= r) {
int64_t term = 0;
if ((r == N && N >= l)) {
if (l <= (N - 1)) {
term = FLOW_CHECKED_MOD(((sum_G_mod_i64_i64_i64((l + m), ((N - 1) + m), M2) - sum_G_mod_i64_i64_i64(((l - m) - 1), (((N - 1) - m) - 1), M2))), (M2));
}
} else {
term = FLOW_CHECKED_MOD(((sum_G_mod_i64_i64_i64((l + m), (r + m), M2) - sum_G_mod_i64_i64_i64(((l - m) - 1), ((r - m) - 1), M2))), (M2));
}
if (term < 0) {
term = (term + M2);
}
large_sum = FLOW_CHECKED_MOD(((large_sum + term)), (M2));
}
}
m = (m + 1);
}
total = FLOW_CHECKED_MOD(((total + (2 * large_sum))), (M2));
int64_t diag = ((2 * min64_i64_i64(FLOW_CHECKED_DIV((N), (2)), isqrt_i64(N))) + 1);
total = FLOW_CHECKED_MOD(((total + FLOW_CHECKED_MOD((diag), (M2)))), (M2));
int64_t ans = FLOW_CHECKED_MOD((FLOW_CHECKED_DIV((total), (2))), (MOD));
printf("%lld\n", ans);
return 0;
}