#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    if(k==1)
        return 1;
    long prev = k-1;
    prev = (prev)*(prev+1)/2;
    long first = 2*prev +1;
    long sum =0;
    for(int i=0; i<k; i++){
        sum += first;
        first +=2;
    }
    return sum;
}

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