10828번 '스택'

import Foundation
 
let input = Int(readLine()!)!
var stack = [Int]()
var commands = [String]()
for _ in 1...input{
    commands.append(readLine()!)
}
for command in commands{
    if(command.contains("push")){
        let number = Int((command.split(separator: " ").last?.description)!)!
        stack.append(number)
    } else {
        switch(command){
        case "pop":
            if let top = stack.popLast(){
                print(top)
            } else {
                print("-1")
            }
        case "size":
            print(stack.count)
        case "empty":
            if(stack.isEmpty){
                print("1")
            } else {
                print("0")
            }
        case "top":
            if let top = stack.last {
                print(top)
            } else {
                print("-1")
            }
        default:
            break
        }
    }
}