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

namespace yukicoder
{
	class pg
	{
		static void Main(string[] args)
		{
			var line1 = Console.ReadLine().Split(' ').ToList();
			string A = line1[0];
			string B = line1[1];
			
			var Anums = A.Select(c => int.Parse(c.ToString())).ToList();
			var Bnums = B.Select(c => int.Parse(c.ToString())).ToList();
			
			if(Anums.Count > Bnums.Count)
			{
				Console.WriteLine(A);
				return;
			}else if(Anums.Count < Bnums.Count)
			{
				Console.WriteLine(B);
				return;
			}
			
			for(int i = 0;i < Anums.Count;i++)
			{
				if(Anums[i] == 4  && Bnums[i] == 7)
				{
					Console.WriteLine(A);
					return;
				}if(Anums[i] == 7  && Bnums[i] == 4)
				{
					Console.WriteLine(B);
					return;
				}else if(Anums[i] > Bnums[i])
				{
					Console.WriteLine(A);
					return;
				}else if( Anums[i] < Bnums[i])
				{
					Console.WriteLine(B);
					return;
				}
			}
		}
	}
}