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


class StuckNumbers
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        //int[] nums = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        List<int> nums = Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToList();
        bool match = false;
        for (int i1 = 0; i1 < nums.Count; i1++)
        {
            for (int i2 = 0; i2 < nums.Count; i2++)
            {
                for (int i3 = 0; i3 < nums.Count; i3++)
                {
                    for (int i4 = 0; i4 < nums.Count; i4++)
                    {
                        int a = nums[i1];
                        int b = nums[i2];
                        int c = nums[i3];
                        int d = nums[i4];
                        if (a != b && a != c && a != d && b != c && b != d && c != d)
                        {
                            String right = "" + a + b;
                            String left = "" + c + d;
                            if (right.Equals(left))
                            {
                                Console.WriteLine(a + "|" + b + "==" + c + "|" + d);
                                match = true;
                            }
                        }
                    }
                }
            }
        }
        if (!match)
        {
            Console.WriteLine("No");
        }
    }
}