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 sum=0;
    long l=0;
        for(int i=k-1;i>0;i--)
            sum=i+sum;
        long s=(sum*2)+1;
        
        for(int j=0;j<k;j++)
        {
           l=l+s;
            s=s+2;
            
        }
        return(l);
        // Return the sum of the elements of the k'th group.
    }

    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();
    }
}