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Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

Examples

Input

2


Output

13
import java.io.*;
import java.util.*;
 
 
public class Main{
static int mod = (int)(Math.pow(10, 9) + 7);
   public static void main(String[] args) {
      MyScanner sc = new MyScanner();
      out = new PrintWriter(new BufferedOutputStream(System.out));
      int n = sc.nextInt();
      out.println(6 * n * (n-1) + 1);
      
      out.close();
   }
static void mergeSort(int[] A){ // low to hi sort, single array only
      int n = A.length;
      if (n < 2) return;
      int[] l = new int[n/2];
      int[] r = new int[n - n/2];
 
      for (int i = 0; i < n/2; i++){
        l[i] = A[i];
      }
 
      for (int j = n/2; j < n; j++){
        r[j-n/2] = A[j];
      }
 
      mergeSort(l);
      mergeSort(r);
      merge(l, r, A);
    }
 
    static void merge(int[] l, int[] r, int[] a){
      int i = 0, j = 0, k = 0;
      while (i < l.length && j < r.length && k < a.length){
        if (l[i] < r[j]){
          a[k] = l[i];
          i++;
        }
        else{
          a[k] = r[j];
          j++;
        }
        k++;
      }
      while (i < l.length){
        a[k] = l[i];
        i++;
        k++;
      }
 
      while (j < r.length){
        a[k] = r[j];
        j++;
        k++;
      }
    }

   

   //-----------PrintWriter for faster output---------------------------------
   public static PrintWriter out;
      
   //-----------MyScanner class for faster input----------
   public static class MyScanner {
      BufferedReader br;
      StringTokenizer st;
 
      public MyScanner() {
         br = new BufferedReader(new InputStreamReader(System.in));
      }
 
      String next() {
          while (st == null || !st.hasMoreElements()) {
              try {
                  st = new StringTokenizer(br.readLine());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          return st.nextToken();
      }
 
      int nextInt() {
          return Integer.parseInt(next());
      }
 
      long nextLong() {
          return Long.parseLong(next());
      }
 
      double nextDouble() {
          return Double.parseDouble(next());
      }
 
      String nextLine(){
          String str = "";
	  try {
	     str = br.readLine();
	  } catch (IOException e) {
	     e.printStackTrace();
	  }
	  return str;
      }

   }
   //--------------------------------------------------------
}

