[백준 1874] 스택 수열 - Python

n = int(input())
cnt=0
stack=list()
result=list()
flag = True
for i in range(n):
    number = int(input())
    while cnt<number:
        cnt+=1
        stack.append(cnt)
        result.append('+')

    if number==stack[-1]:
        stack.pop()
        result.append('-')
    else:
        flag=False
if flag==False:
    print('NO')
else:
    for i in result:
        print(i)