#include <bits/stdc++.h>

using namespace std;

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

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