import sys
input = sys.stdin.readline
N = int(input())
S = input().strip()
M = [0]
P = [0]
for s in S:
    P.append(P[-1])
    M.append(M[-1])
    if s=="+":
        P[-1]+=1
    elif s=="-":
        M[-1]+=1
ans = 0
for i in range(N+1):
    if i<N and S[i]=="0":
        tmp = M[i] + 1 + P[-1]-P[i]
    else:
        tmp = M[i] + P[-1]-P[i]
    ans = max(ans, tmp)
print(ans)