#include <bits/stdc++.h>
#define ll long long int
using namespace std;

int main() {

    ll k, i;
    
    ll sum, start, end, num;
    
    scanf("%lld", &k);
    
    num = k *(k-1) /2 + 1;
    
    start = 1 + (num - 1) * 2;
    
    end = 1 + (num + k - 2) *2;
    
    for(i = start; i <= end ; i +=2) {
        sum += i;
    }
    
    printf("%lld\n",sum);
    return 0;
    
}