#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long long int k) {
    // Return the sum of the elements of the k'th group.
    long long int x=((k-1)*k)/2;
    long long int r1=2*(x+1)-1;
    long long int r2=2*(x+k)-1;
    long long int ans=(k*(r1+r2))/2;
    return ans;
}

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