#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long result = 0;
    long x = 0;
    for(long i=1; i<k; i++) {
        x = x + i;
    }
     x = (x * 2) + 1;
    
    for(long i=0; i < k ; i++) {
        result = result + (x + (2*i));
    }
    
    return result;
}

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