bracket

import sys

def validBrackets(string):
    # maintain balance of string
    bal = 0
    ans = 0
    for i in range(0, len(string)):
        if (string[i] == '('):
            bal += 1
        else:
            ans += 1

    return abs(bal - ans)


def main():
    # read the input String
    f = sys.stdin
    invalid = f.readline().strip()
    print(validBrackets(invalid))


if __name__ == "__main__":
    main()