#include <bits/stdc++.h>

using namespace std;

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

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