#include <bits/stdc++.h>

using namespace std;

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

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