#include <bits/stdc++.h>

using namespace std;

long long int  sumOfGroup(long long  int k) {
    long long int  sum=0;
    long long int first=k*(k-1)+1;
    long long int last=first+(k-1)*2;
    for(long long int i=first;i<=last;i+=2){
        sum+=i;
    }
    return sum;// Return the sum of the elements of the k'th group.
}

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