#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long k) {
    long firstn = ((k-1)*k)+1;
    long long sum=0;
    for(long i=0;i<k;i++){
        sum+=(2*i)+firstn;
    }
    return sum;
}

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