#include <bits/stdc++.h>

using namespace std;

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

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