#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    long s1=k*(k-1)+1,s=0;
    for(int i=0;i<k;i++){
        s+=s1;
        s1=s1+2;
    }
    return s;
}

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