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

L=[]
for i in range(N):
    if (S[i]=='+'):
        L.append(i+10)
    elif S[i]=='0':
        L.append(0)
    else:
        L.append(-10**9+i)

from bisect import *

B=[]
for i in L:
    bi=bisect_left(B,i)
    if (bi==len(B)):
        B.append(i)
    else:
        B[bi]=i

print(len(B))