[Swift] 10773번 : 제로

import Foundation

let k = Int(readLine()!)!

var stack: [Int] = []

for _ in 0..<k {
    
    let n = Int(readLine()!)!
    if n == 0 && !stack.isEmpty {
        stack.removeLast()
        continue
    }
    stack.append(n)
}


print(stack.reduce(0, +))