import sys
input = sys.stdin.readline

N = int(input())
S = input().rstrip()
L = 30
dp0 = [-10**18] * L
dp1 = [-10**18] * L
dp0[0] = 0
for i in range(N):
    for j in range(L-1):
        dp1[j+1] = max(dp1[j+1], dp0[j])
    ndp0 = [-10**18] * L
    ndp1 = [-10**18] * L
    if S[i] != "-":
        for j in range(L):
            ndp0[j] = max(ndp0[j], dp0[j]+1)
            if dp1[j]-1 >= 0:
                ndp1[j] = max(ndp1[j], dp1[j]-1)
    if S[i] != "+":
        for j in range(L):
            if dp0[j]-1 >= 0:
                ndp0[j] = max(ndp0[j], dp0[j]-1)
            ndp1[j] = max(ndp1[j], dp1[j]+1)
    dp0 = ndp0
    dp1 = ndp1
    for j in range(L):
        dp0[j] = max(dp0[j], dp1[j])
ans = 0
while dp0[ans] < 0:
    ans += 1
print(ans)