#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  int N;
  cin>>N;
  int ans = 0;
  int mod = 1e9+7;
  for(int i=0;i<N;i++){
      int a,b;
      cin>>a>>b;
      b %= mod;
      ans += ((a+1)/2)%mod*b%mod;
      ans %= mod;
  }
  cout<<ans<<endl;
}