#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    if(k==1)return 1;
    else if(k==2)return 8;
    else {
        long long int n=k;n=n*(n-1)/2;
        n=2*n+1;long long int sum=0;
        for(int i=0;i<k;i++){
            sum=sum+n;
            n+=2;
        }
        return sum;
    }
}

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