using System;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
        const string pattern = "^(\\d{1,4}(\\.\\d{1,3})?)(?<!^[0\\.]+)$";
		Console.WriteLine(Regex.IsMatch("0", pattern));
    	Console.WriteLine(Regex.IsMatch("0.0", pattern));
    	Console.WriteLine(Regex.IsMatch("00", pattern));
    	Console.WriteLine(Regex.IsMatch("0.1", pattern));
    	Console.WriteLine(Regex.IsMatch("1.23", pattern));
        Console.WriteLine(Regex.IsMatch("1.00", pattern));
	}
}

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