#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
const int MOD=1e9+7;
int main() {
  long long n,c,d,ans=0;
  cin >> n;
  for(int i=0; i<n; i++) {
      cin >> c >> d;
      if(c%2==0) {
          c/=2;
          ans+=(c%MOD)*(d%MOD);
      }
      else {
          c++;
          c/=2;
          ans+=(c%MOD)*(d%MOD);
      }
  }
  cout << ans%MOD << endl;
}