import java.util.*;
import java.io.*;
class NumberGroup {
static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    static StringTokenizer st = null;
    
    static String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }
    
    static int nextInt() {
        return Integer.parseInt(next());
    }
    
    static long nextLong() {
        return Long.parseLong(next());
    }
 
    public static void main(String args[]) {
        try {
                long k=nextInt();
                long a=k*(k-1);
                a=a+1;
                long sum=0;
                while(k-->0)
                {
                    sum+=a;
                    a+=2;
                }
                System.out.println(sum);
            bw.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}