using System.Collections.Generic;
using System;
using System.Drawing;
namespace yukicoder
{
    class Program
    {

        static void Main(string[] args)
        {
            var s = Console.ReadLine();
            var str = Console.ReadLine();
            
            List<int> list = new List<int>(6);
            List<int> list2 = new List<int>(6);
            int x = 0;

            while (s.Substring(x, 1) == str.Substring(x, 1))
            {
                x++;
            }

            int a = int.Parse(s.Substring(x, 1));
            int b = int.Parse(str.Substring(x, 1));



            if (a < b)
            {
                Console.WriteLine("NO");
            }
            else
            {
                Console.WriteLine("YES");
            }
        }
    }
}