#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>

#define ALL(x) (x).begin(),(x).end()
#define REP(i,n) for(int i = 0;i < (n);i++)
#define PI 3.14159265359
#define MOD 1000000007

using namespace std;

int main(){
    long long n,ans = 0;
    cin >> n;
    REP(i,n){
        long long c,d;
        cin >> c >> d;
        c = (c+1)/2;
        ans = (ans + c%MOD * (d%MOD))%MOD;
    }
    cout << ans << endl;
    return 0;
}