#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  const Int MOD = 1e9+7;
  Int ans=0;
  for(Int i=0;i<n;i++){
    Int c,d;
    cin>>c>>d;
    c=(c+1)>>1;
    c%=MOD;d%=MOD;
    ans+=c*d%MOD;
    ans%=MOD;
  }
  cout<<ans<<endl;
  return 0;
}