using System;
using System.Text.RegularExpressions;
using System.IO;
public class Test
{
public static void Main()
{
var data = new string[] {"(123) 556-7890", "123 556 7890", "(123) 556- 7890"};
foreach (var s in data) {
Console.WriteLine(Regex.Replace(s, @"\d(?!\d{0,3}$)", "X"));
}
}
}
dXNpbmcgU3lzdGVtOwp1c2luZyBTeXN0ZW0uVGV4dC5SZWd1bGFyRXhwcmVzc2lvbnM7CnVzaW5nIFN5c3RlbS5JTzsKcHVibGljIGNsYXNzIFRlc3QKewoJcHVibGljIHN0YXRpYyB2b2lkIE1haW4oKQoJewoJCXZhciBkYXRhID0gbmV3IHN0cmluZ1tdIHsiKDEyMykgNTU2LTc4OTAiLCAiMTIzIDU1NiA3ODkwIiwgIigxMjMpIDU1Ni0gNzg5MCJ9OwoJCWZvcmVhY2ggKHZhciBzIGluIGRhdGEpIHsKCQkJQ29uc29sZS5Xcml0ZUxpbmUoUmVnZXguUmVwbGFjZShzLCBAIlxkKD8hXGR7MCwzfSQpIiwgIlgiKSk7CgkJfQoJfQp9