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

public class Solution {

    static long sumOfGroup(int k) {
            if(k==1) return 1;
            int i=1;
            int sum=1;
              while(i<=k){
                  sum+=2;
                  i++;
              }
            int sumF=sum;
            i=1;
               while(i<k){
                    sum+=2;                  
                   sumF += sum;
                   i++;
               }
              return sumF;
    }

    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();
    }
}