n = int(input())
s = input()

m = 0
p = s.count("+")
ans = max(p, s.count("-"))

for i in range(n):
    if s[i] == "-":
        m += 1
    elif s[i] == "+":
        p -= 1
    else:
        ans = max(ans, m+p+1)
print(ans)