#include <bits/stdc++.h>
using namespace std;
using ll=unsigned long long;

const ll N=1000000007;

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