#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    // (2*((k-1)*k)/2+1)
    long nk = (long)k;
    long cur = (2*((nk-1)*nk)/2+1);
    // (cur+cur+(k*2-2))/2*k
    return (cur+cur+(k*2-2))/2*k;
    
}

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