N = int(input())
S = input()

M = [0] * N
P = [0] * N
P[0] = S.count("+")
for i in range(N):
  if S[i] == "-":
    M[i] += 1
  if i != 0:
    if S[i - 1] == "+":
      P[i] -= 1
    M[i] += M[i - 1]
    P[i] += P[i - 1]

ans = 0
for i in range(N):
  a = M[i] + P[i]
  if S[i] == "0":
    a += 1
  ans = max(ans, a)

print(ans)