#include <bits/stdc++.h>

using namespace std;
long long ric,i;
long long k,ans;
int main() {
    cin >> k;
    ric=(((k*(k-1LL))/2LL)+1LL)*2LL-1LL;
    while(k--)
    {
        ans+=ric;
        ric+=2;
    }
    cout << ans << endl;
    return 0;
}