萌新求助 80

#include <bits/stdc++.h>

using namespace std;

unsigned long long ans;
unsigned long long Mod;

int main () {
	Mod = 1e9 + 7;
	unsigned long long r;
	scanf("%llu", &r);
	for (unsigned long long i = 0; i * i <= r; i++) {
		unsigned long long I = i % Mod;
		unsigned long long row = sqrt(r - I * I);
		row %= Mod;
		unsigned long long ans1 = row * (row + 1) * (2 * row + 1) / 6;
		ans1 %= Mod;
		unsigned long long ans2 = I * I;
		ans2 %= Mod;
		ans2 *= row;
		ans2 %= Mod;
		ans += (ans1 + ans2);
		ans %= Mod;
	}
	printf("%llu", ans * 4 % Mod);
	return 0;
}