#include <bits/stdc++.h>

using namespace std;

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

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