using System;

namespace yukicoder
{
    class Program
    {
        static void Main(string[] args)
        {
            string a = Console.ReadLine();
            int ans = 8;
            int count = 0;
            int num1 = a.IndexOf("1", 0);
            int num7 = a.IndexOf("7", 0);
            string str = "";
            str = a.Remove(num1,1);
            str = str.Remove(num7-1, 1);

            if (str.Length >= ans)
            {
                count=str.Length - ans;
            }
            else
            {
                count = ans-str.Length;
            }


            Console.WriteLine(count);
            
        }
    }
}