#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long int k) {
    if (k==1)return 1;
    else {
        long int n= 1 + ((k-1)/2) * (4 + ((k-2)*2));
        long int sum(0);
        
        for(long int i=0;i<k;i++){
            sum+=n;
            n+=2;
        }
        return sum;
    }
}

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