using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "abc@gmail.com";

        bool output = Test(input);

        Console.WriteLine(output);

    }

    private static readonly Regex Pattern = new Regex(@"/^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,63}|[0-9]{1,3})(\]?)$/");

​

    public static bool Test(string input)

    {

        return Pattern.IsMatch(input);

    }

}