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

namespace vizeskannak
{
	class Program
	{
		static void Main(string[] args)
		{
			int[] kannak = new int[3];
			string[] data = Console.ReadLine().Split(' ');
			for (int i = 0; i < 3; i++)
			{
				kannak[i] = int.Parse(data[i]);
			}
			int target = int.Parse(Console.ReadLine());
			Queue<int[]> BFS = new Queue<int[]>();
			BFS.Enqueue(new int[4] { kannak[0] ,0,0,0});
			int minSteps = -1;
			if (kannak[0] == target) minSteps = 0;
			HashSet<string> seen = new HashSet<string>();
			while (BFS.Count>0&&minSteps==-1)
			{
				int[] current = BFS.Dequeue();
				for (int i = 0; i < 3; i++)
				{
					if (current[i]!=kannak[i])
					{
						for (int j = 0; j < 3; j++)
						{
							if (i != j)
							{
								int change = Math.Min(kannak[i] - current[i],current[j]);
								current[i] += change;
								current[j] -= change;
								if (current[i] == target || current[j] == target)
								{
									minSteps = current[3]+1;
									break;
								}
								if (!seen.Contains($"{current[0]}#{current[1]}#{current[2]}"))
								{
									BFS.Enqueue(new int[4] { current[0],current[1],current[2],current[3]+1});
									seen.Add($"{current[0]}#{current[1]}#{current[2]}");
								}
								current[i] -= change;
								current[j] += change;
							}
						}
					}
					if (minSteps != -1) break;
				}
			}
			Console.WriteLine(minSteps);
			Console.ReadKey();
		}
	}
}