using System;
using System.Text;

/*
    User interface contains two types of user input controls: 
    TextInput, which accepts all characters and NumericInput, which accepts only digits.

    Implement the class TextInput that contains:

    Public method void Add(char c) - adds the given character to the current value
    Public method string GetValue() - returns the current value
    Implement the class NumericInput that:

    Inherits TextInput
    Overrides the Add method so that each non-numeric character is ignored
    For example, the following code should output "10":

    TextInput input = new NumericInput();
    input.Add('1');
    input.Add('a');
    input.Add('0');
    Console.WriteLine(input.GetValue());
*/

class TextInput {
    private  System.Text.StringBuilder sb = new System.Text.StringBuilder();
    public void Add(char c){
        sb.Append(c);
    }
    // public string GetValue(){
    //     return currentString.toString();
    // }
    
}



namespace MyCompiler {
    class Program {
        public static void Main(string[] args) {
            Console.WriteLine("Hello world!");
        }
    }
}