s = input()


count = 0
for i in range(len(s)-2):
	if s[i] ==s[i+1]:
		if s[i] != s[i+2]:
			count += 1
	elif s[i] == s[i+2]:
		if s[i] != s[i+1]:
			count += 1
	elif s[i+1] == s[i+2]:
		if s[i] != s[i+1]:
			count += 1
print(count)