class Program
    {
        static void Main(string[] args)
        {
            int[] bagA = Array.ConvertAll(Console.ReadLine().Split(' '), num => int.Parse(num));
            int[] bagB = Array.ConvertAll(Console.ReadLine().Split(' '), num => int.Parse(num));
            int[] turn = Array.ConvertAll(Console.ReadLine().Split(' '), num => int.Parse(num));
            var result = MoveStone(bagA, bagB[0], turn[0]);

            if (result.white < turn[1])
            {
                result.remainder += result.white;
            }
            else
            {
                result.remainder += result.white - turn[1];
            }
                Console.WriteLine(result.remainder);
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="bagA"></param>
        /// <param name="v1"></param>
        /// <param name="v2"></param>
        /// <returns> remainder:移動後のbagAの白色の碁石　white:</returns>
        private static (int remainder , int white) MoveStone(int[] bagA, int v1, int v2)
        {
            int blackRem = v2 - bagA[1];
            if(blackRem < 0)
            {
                blackRem *= -1;
            }
            int remainder = 0;
            if (remainder < 0)
            {
                remainder = 0;
                v1 += bagA[0];
            }
            else
            {
                remainder = bagA[0] - blackRem;
                v1 += blackRem;
            }
                return (remainder, v1);
        }
    }