Difference between compiler on windows and ideone.com

I create two programs and each program has the same task. I create a stack with maximum 10 elements. When You write '+' it means that next, you will insert some number into stack in new line. If the operation is performed successfully program will write line: ':)'. If stack is overflow program will write line: ':('. If You insert '-' it means that program remove last element from the stack and print that element in the console. If stack is empty and you insert '-' program show you ':('.

Example input:

+
1
+
2
+
3
+
4
+
5
+
6
+
7
+
8
+
9
+
0
+
1
-
-
-
-
-
-
-
-
-
-
-

Output:

:)
:)
:)
:)
:)
:)
:)
:)
:)
:(
0
9
8
7
6
5
4
3
2
1
:(

I solved that exercise in two ways; First code: http://ideone.com/WNiNik#comments

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        List<int> list = new List<int>();
        for (; ; )
        {
            char sign = char.Parse(Console.ReadLine());

            switch (sign)
            {
                case '+':
                    {
                        if (list.Count >= 10) Console.WriteLine(":(");
                        else
                        {
                            int number = int.Parse(Console.ReadLine());
                            list.Add(number);
                        }
                        break;
                    }
                case '-':
                    {
                        if (list.Count == 0) Console.WriteLine(":(");
                        else
                        {
                            Console.WriteLine(list[list.Count - 1]);
                            list.Remove(list[list.Count - 1]);
                        }
                        break;
                    }

            }

        }


    }
}

First code works well on Windows but dont works on ideone.com.

Second code: http://ideone.com/InDjF4

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        List<int> list = new List<int>();
        string x;
        while (((x = Console.ReadLine())) != null)
        {
            char sign = char.Parse(x);

            switch (sign)
            {
                case '+':
                    {
                        if (list.Count >= 10) Console.WriteLine(":(");
                        else
                        {
                            int number = int.Parse(Console.ReadLine());
                            list.Add(number);
                            Console.WriteLine(":)");
                        }
                        break;
                    }
                case '-':
                    {
                        if (list.Count == 0) Console.WriteLine(":(");
                        else
                        {
                            Console.WriteLine(list[list.Count - 1]);
                            list.Remove(list[list.Count - 1]);
                        }
                        break;
                    }

            }

        }


    }
}

Second code works well on Windows and ideone.com. I solve that exercise by method of trial and error.Can someone explain me why I get error in my first code and what is the difference between those two codes?