Submission #19370

#	Time	Username	Problem	Language	Result	Execution time	Memory
19370		ilbbke	Σ (kriii4_P2)	C++98	0 / 100	0 ms	1084 KiB

P2

#include<stdio.h>
#define M 1000000007

int m;
long long a,b;

long long back(int x,long long k){
    long long t;
    if(x==0) return 1;
    if(x==1) return k;
    if(x==2) return k*k;
    t=back(x/2,k);
    return x%2?t*t%M*k%M:t*t%M;
}

int main()
{
    scanf("%d",&m);
    int i;
    long long x,y,s=0;
    for(i=1;i<=m;i++){
        scanf("%lld %lld",&b,&a);
        x=back(M-2,b);
        s=(s+(x*a)%M);
    }
    printf("%lld",s);
    return 0;
}

• Subtask 1: 0 / 100