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

const int MOD7 = ( int ) 1e9 + 7;

signed main(){
  int N; cin >> N;
  int ans = 0;
  for( int i = 0; i < N; ++i ){
    int C, D; cin >> C >> D;
    ( ans += 1LL * ( C + 1 ) / 2 * D % MOD7 ) %= MOD7;
  }
  cout << ans << endl;
  return 0;
}