using System;
using System.Text.RegularExpressions;
class Class1
{
[STAThread]
static void Main(string[] args)
{
Regex phoneExp = new Regex( @"^\(\d{3}\)\s\d{3}-\d{4}$" );
string input;
Console.Write( "Enter a phone number: " );
input = Console.ReadLine();
while( phoneExp.Match( input ).Success == false )
{
Console.WriteLine( "Invalid input. Try again." );
Console.Write( "Enter a phone number: " );
input = Console.ReadLine();
}
Console.WriteLine( "Validated!" );
}
}