#include <bits/stdc++.h>

using namespace std;
typedef long long ll ;
ll sumOfGroup(ll k) {
     ll first = k*(k-1)+1;
     int cnt=0;
     ll sum=0;
    while(cnt!=k){
        sum+=first;
        cnt++;
        first+=2;
    }
    return sum;
    
}

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