#include <bits/stdc++.h>

using namespace std;

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

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