#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    if (k == 1) return 1;
    long count = 1;
    long aux = 1;
    while(aux != k){
        for(int i=0;i<aux;i++){
            count += 2;
        }
        aux++;
    }
    long total = 0;
    for(int i=0;i<aux;i++){
        total += count;
        count += 2;
    }
    return total;
}

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