#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    
    long int n,l,u,s=0;
    n=(long)k;
    l=(n*n)-(n-1);
    u=(n*n)+(n-1);
    s=(n*(l+u))/2;
    return s;
    // Return the sum of the elements of the k'th group.
}

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