n=int(input())
s=input()
a=[0]*n
c1=0
c2=n
for i in range(n):
  if s[i]=="+":
    c1+=1
    a[i]=c1
  elif s[i]=="-":
    a[i]=-c2
    c2-=1
q=[n+1]*(n+1)
from bisect import bisect_left
for v in a:
  q[bisect_left(q,v)]=v
while q[-1]==n+1:
  q.pop()
print(len(q))