#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long long int k) {
    long long int n=(k*(k-1))/2;
    long long int sum=0;
    for(long long int i=2*n+1; i<2*(n+k)+1; 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;
}