#include<bits/stdc++.h>
using namespace std;

#define MOD 1000000007

int main(){
    long long ans=0,c,d;
    int N;
    cin >> N;
    while(cin >> c >> d) ans=(ans+(((((c-1)/2+1)%MOD)*(d%MOD))%MOD))%MOD;
    cout << ans << endl;

    return 0;
}