#include <bits/stdc++.h>

using namespace std;
typedef long long int ll;
ll sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    
    ll x=(k-1)*(k)/2+1;
    ll a1=1+(x-1)*2;
    ll a2=a1+(k-1)*2;ll ans=k*(a1+a2)/2;
    return ans;
}

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