journals = input()
new_journal = ""

last_char = None
left_flip_index = None
right_flip_index = None
flips = 0

for index, char in enumerate(journals):
	if last_char is None:
		last_char = char
		continue
	if char == last_char:
		if not left_flip_index:
			left_flip_index = index
		elif left_flip_index and not right_flip_index:
			right_flip_index = index
			flips += 1
			left_flip_index = None
			right_flip_index = None		
		
	last_char = char

if left_flip_index and not right_flip_index:
	flips += 1
print(flips)