[Swift] 백준10773

import Foundation

let K = Int(readLine()!)!

var stack = [Int]()

for _ in 1...K {
    
    let inputNum = Int(readLine()!)!

    if inputNum == 0 && !stack.isEmpty {
        stack.removeLast()
    } else {
        stack.append(inputNum)
    }
}

print(stack.reduce(0, +))