#include <iostream>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <string>
#include <map>
#include <queue>
#include <memory.h>
using namespace std;
const int INF = 2 << 27;
typedef long long ll;
typedef pair<int,int> P;

int main() {
  int n;
  cin >> n;
  ll sum = 0;
  for(int i = 0; i < n; i++) {
    ll c;
    cin >> c;
    c %= 1000000007;
	  ll d;
    cin >> d;
    sum += d * (((c/2)%1000000007) + 1 -(c%2==0?1:0)) % 1000000007;
    sum %= 1000000007;
  }
  cout << sum << endl;
}