S = list(map(int, input()))

count = 0
for i in range(len(S)-1):
  if S[i]!=S[i+1]:
    del S[i],S[i+1]
    count =2+count 
  else:
    if len(S)==i+1:
      print(count)
    else:
  		continue
    
print(count)
   


	

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
