Submission #19588

#	Time	Username	Problem	Language	Result	Execution time	Memory
19588		gs12117	Ω (kriii4_P3)	C++98	100 / 100	0 ms	1084 KiB

P3

#include<stdio.h>
int mod=1000000007;
int p,q,n,m;
int a[110];
int b[110];
long long int f(long long int x,long long int y){
	if(y==0)return 1;
	long long int r=f(x,y/2);
	r*=r;
	r%=mod;
	if(y%2==0)return r;
	r*=x;
	r%=mod;
	return r;
}
int main(){
	int i;
	long long int res=0;
	scanf("%d%d%d%d",&p,&q,&n,&m);
	p=(p-q)*f(p,mod-2)%mod;
	b[1]=p;
	for(i=1;i<n;i++){
		b[i+1]=p*f(((long long int)b[i]*((p+mod-1)%mod)%mod+1)%mod,mod-2)%mod;
	}
	a[n]=1;
	for(i=n-1;i>0;i--){
		a[i]=(long long int)a[i+1]*b[i]%mod;
	}
	a[0]=0;
	printf("%d\n",a[m]);
}

• Subtask 1: 100 / 100