using System;
using System.Linq;
namespace ConsoleTest
{
    public class Program
    {
        public static void Main()
        {
            string s = Console.ReadLine();
            var a = s.ToCharArray().Where(x => x == '7' || x == '4').ToArray().Length.ToString().ToCharArray();
            Console.WriteLine(a.Where(x => x != '7' && x != '4').ToArray().Length == a.Length ? "NO" : "YES");
        }
    }
}