using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string str = "11&222&&333&&&44444&&&&55&&&&&";
		str = Regex.Replace(str, "&((?:(?<2>&)(?<-2>&)?)*)", "$1$2");
		Console.WriteLine(str);
	}
}