def main():
    with open("input.txt") as f:
        stream = list(f.read())

    valid_characters = ['{', '}']
    filtered_stream = []
    state = True

    for index, char in enumerate(stream):
        if char == '<' and isnt_not(index, stream):
            state = False

        if state == True and char in valid_characters:
            filtered_stream.append(char)

        if char == '>' and isnt_not(index, stream):
            state = True

    print(get_score(filtered_stream))


def isnt_not(index, stream):
    '''Check if the previous characters cancel the current character'''
    if stream[index - 1] != '!':
        return True
    else:
        i = 0
        while stream[(index - 1) - i] == '!':
            i += 1
        return i % 2 == 0


def get_score(filtered_stream):
    '''return total score from list of brackets'''
    score, m = 0, 0
    for char in filtered_stream:
        if char == '{':
            m += 1
            score += m
        elif char == '}':
            m -= 1
    return score


if __name__ == '__main__':
    main()