#include <bits/stdc++.h>
#define fastIO (cin.tie(0), cout.tie(0), ios::sync_with_stdio(false))
#define precise(i) fixed << setprecision(i)
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;

const int MOD = 1000000007;
int main() {
  fastIO;
  int n;
  cin >> n;

  long long cnt = 0;
  for (int i = 0; i < n; i++) {
    long long c, d;
    cin >> c >> d;
    cnt = ((cnt % MOD) + ((c + 1) / 2) % MOD * (d % MOD)) % MOD;
  }

  cout << cnt << endl;
  return 0;
}