#include <bits/stdc++.h>

using namespace std;

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

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