#include <bits/stdc++.h>

using namespace std;

unsigned long long sumOfGroup(int k) {
    unsigned long long num = (unsigned long long)k*(unsigned long long)(k-1)+1; // begin of group
    unsigned long long sum = 0;
    for(int i = 0; i < k; ++i)
    {
        sum += num;
        num += 2;
    }
    return sum;
}

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