답안 #19870

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
19870	2016-02-25T06:27:27 Z	xdoju	팔찌 (kriii4_V)	C++14	6 / 100	1000 ms	13724 KB

V

#include <cstdio>
#include <cmath>
#include <vector>
using namespace std;

const int MOD = 1000000007ll;

int modpow(int r, int n) {
	int ret = 1;
	while (n > 0) {
		if (n % 2 > 0) {
			ret = ((long long)ret * r) % MOD;
		}
		r = ((long long)r * r) % MOD;
		n /= 2;
	}
	return ret;
}

int modinv(int n) {
	return modpow(n, MOD - 2);
}

int modprod(int a, int b) {
	a = a % MOD;
	b = b % MOD;
	return ((long long)a * b) % MOD;
}

int modprod(int a, int b, int c) {
	c = c % MOD;
	return (modprod(a, b) * (long long)c) % MOD;
}

int moddiv(int a, int b) {
	return ((long long)a * modinv(b)) % MOD;
}

const int N = 1000000;
int lp[N + 1];
int phi[N + 1];
vector<int> pr;

void sieve() {
	phi[1] = 1;
	for (int i = 2; i <= N; ++i) {
		if (lp[i] == 0) {
			lp[i] = i;
			phi[i] = i - 1;
			pr.push_back(i);
		}
		else {
			if (lp[i] == lp[i / lp[i]]) {
				phi[i] = phi[i / lp[i]] * lp[i];
			}
			else {
				phi[i] = phi[i / lp[i]] * (lp[i] - 1);
			}
		}
		for (int j = 0; j < (int)pr.size() && pr[j] <= lp[i] && i * pr[j] <= N; ++j) {
			lp[i * pr[j]] = pr[j];
		}
	}
}

int mpow[N + 1];

void proc() {
	sieve();

	int n, k;
	scanf("%d %d", &n, &k);

	for (int i = 1; i <= n; ++i) {
		mpow[i] = modpow(k, i);
	}

	int ans = 1;
	for (int i = 1; i <= n; ++i) {
		int t = 0;

		int lmt = (int)(sqrt(i) + 0.00001);
		for (int p = 1; p <= lmt; ++p) {
			if (i % p != 0) {
				continue;
			}
			int q = i / p;

			t = (t + modprod(mpow[q], phi[p])) % MOD;
			if (p != q) {
				t = (t + modprod(mpow[p], phi[q])) % MOD;
			}
		}
		t = moddiv(t, i);


		int u = 0;
		if (i % 2 == 0) {
			u = moddiv(t, 2);
			int v = modprod(k + 1, mpow[i / 2]);
			v = moddiv(v, 4);
			u = (u + v) % MOD;
		}
		else {
			u = moddiv(t, 2);
			int v = mpow[(i + 1) / 2];
			v = moddiv(v, 2);
			u = (u + v) % MOD;
		}

		ans = (ans + u) % MOD;
	}
	printf("%d", ans);
}

int main() {
	//freopen("input.txt", "r", stdin);
	proc();
	return 0;
}

Subtask #1

6.0 / 6.0

#	결과	실행 시간	메모리	Grader output
1	Correct	15 ms	13724 KB	Output is correct
2	Correct	16 ms	13724 KB	Output is correct
3	Correct	13 ms	13724 KB	Output is correct
4	Correct	12 ms	13724 KB	Output is correct
5	Correct	15 ms	13724 KB	Output is correct
6	Correct	15 ms	13724 KB	Output is correct
7	Correct	12 ms	13724 KB	Output is correct
8	Correct	15 ms	13724 KB	Output is correct
9	Correct	15 ms	13724 KB	Output is correct
10	Correct	16 ms	13724 KB	Output is correct
11	Correct	15 ms	13724 KB	Output is correct
12	Correct	15 ms	13724 KB	Output is correct
13	Correct	15 ms	13724 KB	Output is correct
14	Correct	16 ms	13724 KB	Output is correct
15	Correct	15 ms	13724 KB	Output is correct
16	Correct	15 ms	13724 KB	Output is correct
17	Correct	16 ms	13724 KB	Output is correct
18	Correct	15 ms	13724 KB	Output is correct
19	Correct	11 ms	13724 KB	Output is correct
20	Correct	15 ms	13724 KB	Output is correct

Subtask #2

0.0 / 94.0

#	결과	실행 시간	메모리	Grader output
1	Correct	16 ms	13724 KB	Output is correct
2	Correct	16 ms	13724 KB	Output is correct
3	Correct	13 ms	13724 KB	Output is correct
4	Correct	123 ms	13724 KB	Output is correct
5	Execution timed out	1000 ms	13724 KB	Program timed out
6	Halted	0 ms	0 KB	-