using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(!IsValid(""));

        Console.WriteLine(!IsValid("010"));

        Console.WriteLine(!IsValid("001"));

        Console.WriteLine(!IsValid("12a"));

        Console.WriteLine(!IsValid("123"));

        Console.WriteLine(!IsValid("1234"));

        Console.WriteLine(IsValid("12"));

    }

    static bool IsValid(string input)

    {

        return !string.IsNullOrEmpty(input) && input.Length < 3 && !input.StartsWith("0") && input.All(char.IsDigit); 

    }

}