S = input()
list_S = []
count = 0
total = 0
for i in range(len(S)):
a = S[i:i+1]
list_S.append(a)
for i in range(len(list_S)-1):
if list_S[i] != list_S[i+1] :
count+=1
if count%2==0:
total = count//2
else:
total = count//2 +1
print(total)