#include<bits/stdc++.h>

using namespace std;

int main()
{
    long long int k;
    cin>>k;
    long long int temp=k-1;
    temp=((temp)*(temp+1))/2;
    temp+=1;
    long long int a=2*temp-1;
    long long int sum;
    
    sum=(k)*(a+(k-1));
    
    cout<<sum<<endl;
    return 0;
}