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

public class Solution {

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

    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();
    }
}