#include <bits/stdc++.h>

using namespace std;
#define ll long long
ll sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    ll id = (k*(k-1))/2;
    ll now = 2*id+1,ret = 0;
    for(int i  = 0; i< k; i++){
        ret+= now;
        now+=2;
    }
    return ret;
}

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