[백준] 스택수열 1874 Python

N = int(input())
obj = []
stack = []
result = []
idx = 0
 
for i in range(N):
    obj.append(int(input()))
 
for i in range(1, N+1):
    stack.append(i)
    result.append("+")
 
    while idx < N and len(stack) != 0 and obj[idx] == stack[-1]:
        stack.pop()
        result.append("-")
        idx += 1
 
if not stack:
    for i in result:
        print(i)
else:
    print("NO")