https://www.acmicpc.net/problem/10773

계산 도와주며 0외치면 삭제 스택 합 구하기

import sys
input = sys.stdin.readline

k = int(input())
stack = []

for _ in range(k):
    num = int(input())

    if num == 0:
        stack.pop()
    else:
        stack.append(num)

print(sum(stack))