#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<map>
#include<vector>
using namespace std;
typedef long long int ll;

int main(){

  int n;
  cin >> n;
  ll ans=0;
  vector<ll> c(n), d(n);
  for(int i=0; i<n; i++){
    cin >> c[i] >> d[i];
    ans+=(c[i]/2+c[i]%2)*d[i];
  }
  cout << ans%(1000000000+7) << endl;
  
  return 0;
}