#include <bits/stdc++.h>

using namespace std;

const int MOD = 1e9 + 7;

int main()
{
  int N;
  cin >> N;
  int ret = 0;
  while(N--) {
    long A, B;
    cin >> A >> B;
    (ret += (A + 1) / 2 % MOD * B % MOD) %= MOD;
  }
  cout << ret << endl;
}