C# 백준 10828번 문제 스택

using System;
using System.Collections;
using System.Collections.Generic;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            int cnt = int.Parse(Console.ReadLine());
            Stack stack_1 = new Stack(cnt);
            
            for (int i = 0; i < cnt; i++)
            {
                string[] cmd = Console.ReadLine().Split();

                if (cmd[0] == "push")
                {
                    stack_1.Push(cmd[1]);
                }
                else if (cmd[0] == "pop")
                {
                    if (stack_1.Count == 0)
                    {
                        Console.WriteLine("-1");
                    }
                    else
                    {
                        Console.WriteLine(stack_1.Pop());
                    }
                }
                else if (cmd[0] == "size")
                {
                    Console.WriteLine(stack_1.Count);
                }
                else if (cmd[0] == "empty")
                {
                    if (stack_1.Count == 0)
                    {
                        Console.WriteLine("1");
                    }
                    else
                    {
                        Console.WriteLine("0");
                    }
                }
                else if (cmd[0] == "top")
                {
                    if(stack_1.Count == 0)
                    {
                        Console.WriteLine("-1");
                    }
                    else
                    {
                        Console.WriteLine(stack_1.Peek());
                    }
                }
            }
        }      
    }
}