#include <iostream>
using namespace std;
#define rep(i,q) for(int i = 0; (q) > i; i++)
#define MOD 1000000007
int main(){
  int N;cin>>N;
  long long sm = 0;
  rep(i,N){
    long long C,D;cin>>C>>D;
    sm = (sm + (((C+1)/2)*D))%MOD;
  }
  cout << sm << endl;
}