#include <bits/stdc++.h>

using namespace std;

typedef long long LL;

LL gauss(LL N) { return (N * (N + 1) / 2); }

LL solve(LL N)
{
    LL p = gauss(N - 1) + 1;
    LL u = gauss(N);
    LL ans = 0;
    p = 2 * p - 1;
    u = 2 * u - 1;
    
    for(LL i = p; i <= u; i += 2)
        ans += i;
    return ans;
}

int main() {
    int k;
    cin >> k;
    LL ans = solve(k);
    cout << ans;
    return 0;
}