Submission #20116

#	Time	Username	Problem	Language	Result	Execution time	Memory
20116		sui	Ω (kriii4_P3)	C++14	0 / 100	0 ms	1720 KiB

P3

#define _CRT_SECURE_NO_WARNINGS // scanf(), gets() (needed for Visual C++)

//#define NDEBUG
#include <cassert>

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <functional>
#include <string>
#include <vector>

#include <queue>
#include <set>
#include <map>
#include <unordered_map>
#include <stack>
#include <deque>

using namespace std;

#define MEMSET(x, WITH) memset(x, (WITH), sizeof(x))
#define FOR(i, E) for(int i=0; i<(E); i++)
#define REP(i, LO, HI) for(int i=(LO); i<=(HI); i++)

#define GETINT(x) scanf("%d", &x)
#define GETDBL(x) scanf("%lf", &x)
#define GETSTR(x) scanf("%s", x)
#define NEWINT(x) int x; scanf("%d", &x)
#define NEWDBL(x) double x; scanf("%lf", &x)
#define NEWLN putchar('\n')

#ifdef _WIN32
#define popcnt __popcnt
#else
#define popcnt __builtin_popcount
#endif

typedef long long ll;
//const ll MOD = 1000000007;
//const double PI = atan(1) * 4;







const ll MOD = 1000000007;

ll powerMod(ll a, ll n) {
	ll ans = 1;
	for (int i=62; i>=0; i--) {
		ans = ans * ans % MOD;
		if ((n>>i)&1)
			ans = ans * a % MOD;
	}
	return ans;
}
ll inv(ll a) {
	return powerMod(a, MOD-2);
}



// The probability to go down: Q/P
// The probability to go up: 1 - Q/P

ll P, Q, N, K;
// 0 <= Q <= P

int main() {
	cin >> P >> Q >> N >> K;
	if (Q == P) {
		puts("0"); return 0;
	}
	if (Q == 0) {
		puts("1"); return 0;
	}


	ll r = Q * inv(P-Q) % MOD;
	if (r == 1) {
		cout << K * inv(N) % MOD << endl; return 0;
	}


	ll a = (r-1+MOD) * inv(powerMod(r, N)-1+MOD) % MOD;
	ll ans = a * ((powerMod(r, K)-1+MOD)%MOD) % MOD * inv(r-1+MOD) % MOD;
	cout << ans << endl;




	return 0;
}

• Subtask 1: 0 / 100