using System;

public class Program

{

    public static void Main()

    {

        string username = "[MjgvMDEvMjAyMCAxMjoyMg==] admin@wp.com";

        string result = !string.IsNullOrEmpty(username) && username.Contains("]") ? username.Substring(username.IndexOf(']') + 1) : username;

        Console.WriteLine(username + ":" + result);

    }

}