using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string[] lines = { 
            "Foo 12;",
            "Foo 5534;",
            "Foo 1;"
            };
        foreach (String line in lines) {
            Console.WriteLine(Regex.Replace(line, @"(Foo) \d+;", "$1 NUM;"));              
        }
	}
}