using System;

using System.Text.RegularExpressions;       

public class Program

{

    public static void Main()

    {

        Regex r = new Regex("^[a-zA-Z0-9]*$");

        System.Console.WriteLine(r.IsMatch("abcAbc123"));

        System.Console.WriteLine(r.IsMatch(" abcAbc123"));

        System.Console.WriteLine(r.IsMatch("abcAbc123 "));

        System.Console.WriteLine(r.IsMatch("abc Abc123"));

        System.Console.WriteLine(r.IsMatch(" abc Abc 123 "));

        System.Console.WriteLine(r.IsMatch("Ab125cAbc123"));

    }

}