using System;

class Program
{
    static void Main()
    {
        var tmp = Console.ReadLine().Split();
        var a = tmp[0];
        var b = tmp[1];

        a = a.PadLeft(Math.Max(a.Length, b.Length), '0');
        b = b.PadLeft(Math.Max(a.Length, b.Length), '0');

        for(int i = 0; i < a.Length; i++)
        {
            if (a[i] == '4' && b[i] == '7')
            {
                Console.WriteLine(tmp[0]);
                break;
            }
            else if (a[i] == '7' && b[i] == '4')
            {
                Console.WriteLine(tmp[1]);
                break;
            }

            if (a[i] > b[i])
            {
                Console.WriteLine(tmp[0]);
                break;
            }
            else if (a[i] < b[i])
            {
                Console.WriteLine(tmp[1]);
                break;
            }
        }
    }
}