#include <bits/stdc++.h>

using namespace std;

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

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