#include <iostream>
using namespace std;

using ll = unsigned long long int;

int main(void){
    // Here your code !
    int n;
    cin >> n;
    ll res = 0;
    
    for(int i = 0; i < n; i++){
        ll c,d;
        cin >> c >> d;
        
        c %= 1000000007;
        d %= 1000000007;
        
        c = (c+1)/2;
        
        res += c*d;
        
        res %= 1000000007;
    }
    
    cout << res << endl;
    
}