#include <stdio.h>

#define MOD 1000000007

long long power(long long a, int n);

int main() {
    int M;
    scanf("%d",&M);

    long long ans = 0;
    while(M--) {
        long long N, S;
        scanf("%lld %lld",&N, &S);
        ans += (S*power(N, MOD-2))%MOD;
    }

    printf("%lld\n", ans%MOD);

    return 0;
}

long long power(long long a, int n) {
    if(n==0) return 1;
    if(n==1) return a%MOD;

    long long temp = power(a, n/2);
    long long result = temp*temp%MOD;

    if(n%2) result = result*a%MOD;

    return result;
}