pocet = int(input())
brack = input()
expres = "("
for i in range(pocet-1):
	if brack[i] == "(":
		if brack[i+1] == ")":
			expres += "1"
	elif brack[i+1] == "(":
		expres += "*"
	else:
		expres += "+1"
	expres += brack[i+1]

print(eval(expres))