//Normal

#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

void print(auto a){
  cout << a;
}

void prints(auto a){
  cout << a << " ";
}

void prints(){
  cout << " ";
}

void printl(auto a){
  cout << a << endl;
}

void printl(){
  cout << endl;
}

void fix(int n){
  cout << fixed << setprecision(n);
}

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

  ll ans = 0;
  for(int i = 0; i < N; i++){
    ll C, D; cin >> C >> D;

    ll E = (C+1)/2;

    ans += D*E;

    ans %= 1000000007;
  }

  printl(ans);

  return 0;
}