#include <bits/stdc++.h>

using namespace std;
typedef unsigned long long int ll;

long sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    ll i=1,n=0,r=2,a=1,s=0,j;
    i=(k*(k-1))/2;
    i=1+((i-1)*2);i+=2;
    j=(k*(k+1))/2;
    j=1+((j-1)*2);
    for(ll p=i;p<=j;p+=2)s+=p;
    return s;
}

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