Submission #19888

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
19888	2016-02-25T06:46:16 Z	xdoju	팔찌 (kriii4_V)	C++14	6 / 100	1000 ms	13700 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;
}

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

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

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

inline 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 geoseries(int k, int cnt) {
	if (k == 1) {
		return cnt;
	}
	if (cnt <= 0) {
		return 0;
	}

	int ret = (modpow(k, cnt) - 1 + MOD) % MOD;
	ret = modprod(ret, k);
	return moddiv(ret, k - 1);
}

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);
	}

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

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

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

	int ans = moddiv(ssum % MOD, 2);

	int x = moddiv(modprod(k + 1, geoseries(k, n / 2)), 4);
	int y = moddiv(geoseries(k, (n + 1) / 2), 2);

	ans = (ans + 1) % MOD;
	ans = (ans + x) % MOD;
	ans = (ans + y) % MOD;

	printf("%d", ans);
}

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

Subtask #1

6.0 / 6.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	14 ms	13700 KB	Output is correct
2	Correct	12 ms	13700 KB	Output is correct
3	Correct	11 ms	13700 KB	Output is correct
4	Correct	12 ms	13700 KB	Output is correct
5	Correct	16 ms	13700 KB	Output is correct
6	Correct	17 ms	13700 KB	Output is correct
7	Correct	16 ms	13700 KB	Output is correct
8	Correct	12 ms	13700 KB	Output is correct
9	Correct	16 ms	13700 KB	Output is correct
10	Correct	10 ms	13700 KB	Output is correct
11	Correct	10 ms	13700 KB	Output is correct
12	Correct	10 ms	13700 KB	Output is correct
13	Correct	15 ms	13700 KB	Output is correct
14	Correct	11 ms	13700 KB	Output is correct
15	Correct	11 ms	13700 KB	Output is correct
16	Correct	15 ms	13700 KB	Output is correct
17	Correct	11 ms	13700 KB	Output is correct
18	Correct	15 ms	13700 KB	Output is correct
19	Correct	15 ms	13700 KB	Output is correct
20	Correct	11 ms	13700 KB	Output is correct

Subtask #2

0.0 / 94.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	11 ms	13700 KB	Output is correct
2	Correct	16 ms	13700 KB	Output is correct
3	Correct	16 ms	13700 KB	Output is correct
4	Correct	95 ms	13700 KB	Output is correct
5	Execution timed out	1000 ms	13700 KB	Program timed out
6	Halted	0 ms	0 KB	-