#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long temp=k-1;
    long sum=(temp*(temp+1))/2;
    long a=1+(sum)*2;
    long l=1+(sum+k-1)*2;

    long ans=(k*(a+l))/2;
    return ans;
    
}

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