#include <bits/stdc++.h>

using namespace std;

unsigned long long int sumOfGroup(unsigned long long int k) {
    
    unsigned long long int s= ((k-1)*(k)/2),t=1,sum=0;
    
    while(s--)
        t=t+2;
    
    while(k--)
    {
        sum=sum+t;
        t=t+2;
       
    }
    
    return sum;
    
    
    
}

int main() {
   unsigned long long int k;
    cin >> k;
    unsigned long long int answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}