using System;

// TODO: your MyStack class goes here

class Program {
    static string ReverseString(string input) {
        MyStack stack = new MyStack();

        string output = "";

        // TODO: Do something here

        return output;
    }

    static void Main(string[] args) {
        Console.WriteLine(ReverseString("hello")); // olleh
        Console.WriteLine(ReverseString("(a+b)*(c+d)")); // )d+c(*)b+a(
    }
}