제출 #19814

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
19814		tonyjjw	팔찌 (kriii4_V)	C++14	6 / 100	1000 ms	93328 KiB

V

//*
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <numeric>
#include <functional>
#define MOD 1000000007
#define MAX 0x3f3f3f3f
#define MAX2 0x3f3f3f3f3f3f3f3fll
#define ERR 1e-10
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#pragma warning(disable:4996)
using namespace std;

typedef long long ll;
typedef long double ldb;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;

int n, m;
vector<int> d[1040000];
ll pi[1040000];
int comp[1040000];

ll mul_inv(ll a, ll b=MOD)
{
	ll b0=b, t, q;
	ll x0=0, x1=1;
	if(b == 1) return 1;
	while(a > 1)
	{
		q=a/b;
		t=b, b=a%b, a=t;
		t=x0, x0=x1-q*x0, x1=t;
	}
	if(x1 < 0) x1+=b0;
	return x1;
}


ll modpow(ll x, ll y)
{
	ll ans=1;
	while(y)
	{
		if(y%2) ans*=x, ans%=MOD;
		x*=x, x%=MOD, y/=2;
	}
	return ans;
}

int main()
{
	int i, j, k;
	cin>>n>>m;
	for(i=1;i<=n;i++) pi[i]=i;
	for(i=1;i<=n;i++)
	{
		for(j=i;j<=n;j+=i)
		{
			if(j != i && i >= 2) comp[j]=1;
			if(i >= 2 && !comp[i])
			{
				pi[j]/=i, pi[j]*=i-1;
			}
			d[j].push_back(i);
		}
	}
	ll ans=0;
	for(i=1;i<=n;i++)
	{
		ll neck=0;
		for(auto e : d[i])
		{
			neck+=pi[e]*modpow(m, i/e)%MOD;
			neck%=MOD;
		}
		neck*=mul_inv(i*2, MOD);
		neck%=MOD;
		if(i%2 == 0)
		{
			neck+=mul_inv(4, MOD)*(m+1)%MOD*modpow(m, i/2)%MOD;
			neck%=MOD;
		}
		else
		{
			neck+=mul_inv(2, MOD)*modpow(m, (i+1)/2)%MOD;
			neck%=MOD;
		}
		ans+=neck, ans%=MOD;
	}
	ans++;
	ans%=MOD;
	cout<<ans;
	return 0;
}
//*/

• Subtask 1: 6 / 6
• Subtask 2: 0 / 94