using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static bool fillUtil(int[] res, int curr, int n)
        {
            if (curr == 0) return true;
            int i;
            for (i = 0; i < 2 * n - curr - 1; i++)
            {
                if (res[i] == 0 && res[i + curr + 1] == 0)
                {
                    res[i] = res[i + curr + 1] = curr;
                    if (fillUtil(res, curr - 1, n))
                        return true;

                    res[i] = res[i + curr + 1] = 0;
                }
            }
            return false;
        }
        static void fill(int n)
        {
            int[] res = new int[2 * n];

            int i;
            for (i = 0; i < 2 * n; i++)
                res[i] = 0;
            if (fillUtil(res, n, n))
            {
                for (i = 0; i < 2 * n; i++)
                    Console.Write(res[i]);
            }
            else
                Console.Write("Not Possible");
        }

        static void Main(string[] args)
        {
            Console.Write("3: ");
            fill(3);
            Console.Write("\n\n2: ");
            fill(2);
            Console.Write("\n4: ");
            fill(4);
            Console.Write("\n\n");
            Console.ReadKey();
        }
    }
}