Submission #19330

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
19330	2016-02-24T09:49:59 Z	imsifile	Ω (kriii4_P3)	C++	0 / 100	0 ms	1084 KB

P3

#include<stdio.h>
#define mod 1000000007

typedef long long lld;
lld a, b, sum;

lld exp(lld a, lld b){
	if(b==0)return 1;
	lld k=exp(a, b/2);
	k=(k*k)%mod;
	if(b%2)k=(k*a)%mod;
	return k;
}

int n, k;
lld p, q, pq, npq, dy[111], re;

int main(){
	int n, i;
	scanf("%lld%lld%d%d", &p, &q, &n, &k);
	pq = q*exp(p,mod-2)%mod, npq = p*exp(p-q,mod-2)%mod;
	dy[1]=1;
	for(i=1; i<n; i++)dy[i+1] = (dy[i] - pq*dy[i-1]%mod + mod)*npq%mod;
	re = exp(dy[n],mod-2);
	printf("%lld", dy[k]*re%mod);
	return 0;
}

Subtask #1

0.0 / 100.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	0 ms	1084 KB	Output is correct
2	Correct	0 ms	1084 KB	Output is correct
3	Correct	0 ms	1084 KB	Output is correct
4	Incorrect	0 ms	1084 KB	Output isn't correct
5	Halted	0 ms	0 KB	-