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

dp = [0, -1<<20, -1<<20]
for i in range(n):
	if s[i] == "+":
		dp[2] = max(dp) + 1
	elif s[i] == "0":
		dp[1] = max(dp[0] + 1, dp[1])
	else:
		dp[0] += 1
print(max(dp))