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

public class Solution {

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

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