/* -*- coding: utf-8 -*-
 *
 * 146.cc: No.146 試験監督(1) - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

typedef long long ll;
const ll MOD = 1000000007;

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;

  ll sum = 0;

  while (n--) {
    ll ci, di;
    cin >> ci >> di;

    sum = (sum + ((ci + 1) / 2 % MOD) * (di % MOD) % MOD) % MOD;
  }

  printf("%lld\n", sum);
  return 0;
}