import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(int k) {
        long firstInd = ((long)k*(k-1))/2;
        long a = 1+firstInd*2L;
        //System.out.println(a);
        long ans = ((2*a+(k-1)*2)*k)/2;
        return ans;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}