#include<bits/stdc++.h>
using namespace std;

int main()
{
    long long int k;
    cin>>k;
    long long int ans;
    
    long long int lnum , tnum;
    
    lnum = ((k)*(k-1))/2;
    tnum = lnum +k;
    
    ans = (tnum)*(tnum) - (lnum)*(lnum);
    
    cout<<ans<<endl;
    
}