#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long int sum = 0;
    long int end = k;
    end = (end*(end + 1))/2;
    for(long int i = end; i > end - k; --i) {
        sum += (i * 2) - 1;
    }
    
    return sum;
}

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