content: package v009;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
   
   
  public class JoanaandtheOddNumbers_UVa913 {
  	
  	public static void main(String[] args) throws IOException {
  		Scanner sc = new Scanner(System.in);
  		PrintWriter out = new PrintWriter(System.out);
  		
  		while(sc.ready())
  		{
  			int n = (sc.nextInt() + 1) / 2;
  			long idx = 1l * n * n;
  			out.println(get(idx) + get(idx - 1) + get(idx - 2));
  		}
  		out.flush();
  		out.close();
  	}
  	
  	static long get(long n) { return 2 * n - 1; }
  	
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
   
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  	 
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
   
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
   
  		public long nextLong() throws IOException {return Long.parseLong(next());}
   
  		public String nextLine() throws IOException {return br.readLine();}
   
  		public double nextDouble() throws IOException { return Double.parseDouble(next()); }
   
  		public boolean ready() throws IOException {return br.ready();} 
  	}
  } 