# util functions

# debug
$debugFlag = ( ARGV[0] != nil )
p "==== DEBUG MODE ====" if $debugFlag

def pd(str)
  p str if $debugFlag
end

def printd(str)
  print str if $debugFlag
end

# input
inputs = []
lc = 0
while l = $stdin.gets do
  if true
    inputs << l.chomp.split(" ").map(&:to_s)
  else
    inputs << l.chomp.split(" ").map(&:to_i)
  end
  lc += 1
end

# input check
if $debugFlag
  p "--- INPUT (begin) ---"
  inputs.each do |l_i|
    p l_i
  end
  p "--- INPUT (end) ---"
  print "\n"
end

str = inputs[0][0]

# body
if $debugFlag
  p str
end

cnt = 1
skipf = false
for i in 1..str.size-1
  if skipf
    skipf = false
    str[i] = "0"
    cnt += 1
  elsif str[i] == str[i-1]
    skipf = true
  else
    cnt += 1
  end
end

puts cnt
