Submission #19872

#	Time	Username	Problem	Language	Result	Execution time	Memory
19872		gs13068	팔찌 (kriii4_V)	C++98	100 / 100	932 ms	12800 KiB

V

#include <cstdio>

const int p = 1000000007;

int pw(int x, int y)
{
	return y & 1 ? (long long)pw(x, y ^ 1)*x%p : y ? pw((long long)x*x%p, y >> 1) : 1;
}

int a[1000001];
int c[1000001];
int d[1000001];

int main()
{
	int i, j, t1, t2, n, m, r = 0;
	scanf("%d%d", &n, &m);
	for (i = 1; i <= n; i++)
	{
		t1 = (a[i] + pw(m, i)) % p;
		for (j = i; j <= n; j += i)
		{
			a[j] = (a[j] + p - t1) % p;
			d[j] = (d[j] + (long long)t1*(j / i)) % p;
		}
	}
	r = 2;
	for (i = 1; i <= n; i++)
	{
		d[i] = (long long)d[i] * pw(i, p - 2) % p;
		r = (r + d[i]) % p;
		if (i & 1) r = (r + pw(m, i + 1 >> 1)) % p;
		else r = (r + pw(m, i >> 1) * 500000004LL % p * (m + 1)) % p;
	}
	printf("%lld", r * 500000004LL % p);
}

• Subtask 1: 6 / 6
• Subtask 2: 94 / 94