#include <iostream>
using namespace std;

int main(){
   const long long mod = 1e9 + 7;
   int n;
   cin >> n;
   unsigned long long ans = 0,c,d;
   for(int i = 0;i < n;i++){
      cin >> c >> d;
      c = (c + 1) / 2 % mod;
      d %= mod;
      ans += c * d;
      ans %= mod;
   }
   cout << ans << endl;
}