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

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var na = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var nb = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var nc = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var Aw = na[0];
            var Ab = na[1];
            var Bw = nb[0];
            var Bb = nb[1];
            var Cc = nc[0];
            var Cd = nc[1];
            var dC = Cc > Ab ? Cc - Ab : 0;
            Aw -= dC;
            Bw += dC;
            var dD = Cd < Bw ? Cd : Bw;
            Aw += dD;
            Bw -= dD;
            Console.WriteLine(Aw);
            Console.ReadLine();
        }
    }
}