#!/usr/bin/python3

file = [i.rstrip() for i in open("input").readlines()]
j = 0
count = 0
for i in file[0]:
    if i == "(":
        j += 1
    elif i == ")":
        j -= 1

    count += 1

    if j == -1:
        print("fin: count = " + str(count))
        exit()


print(j)