S=input()

prev = None
cnt=0
cnt_lst=list()
for char in S:
  if char == prev :
    cnt+=1
    cnt_lst[-1] = cnt
    
  else:
    cnt_lst.append(1)
    cnt=1
ans =sum([cnt//3*2 for cnt in cnt_lst])

cnt_lst = [cnt%3 for cnt in cnt_lst]

for index in range( len(cnt_lst)):
  if index>0:
    if cnt_lst[index]>0:
      ans+=1
      if cnt_lst[index]+cnt_lst[index-1]==4:
        ans+=1
        cnt_lst[index]=0
print(ans)
