#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    
    if (k==1) return 1;
    if (k==2) return 8;
    
   long result=0, start=1, index=1;
    while(index < k)
    {
        start += index*2;
        index++;
    }
    for (int i=0; i<k; i++)
    {
        result += start;
        start += 2;
    }
    return result;
}

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