#include <bits/stdc++.h>
using namespace std;

const int64_t MOD = 1e9 + 7;

int main() {
  int N; cin >> N;
  int64_t ans = 0;
  for (int i = 0; i < N; i++) {
    int64_t c, d;
    cin >> c >> d;
    ans = ((ans % MOD) + (((c + 1) / 2 % MOD) * (d % MOD)) % MOD) % MOD;
  }
  cout << ans << endl;
  return 0;
}