begin
s = readline().chomp
for i in 0..(s.length-1) do
  for j in (i+2)..(s.length) do
  inlist = Array.new(26, 0)
  outlist = Array.new(26, 0)
  flg = true
    for k in 0..(s.length-1) do
      c = s[k].codepoints[0] - 97
      if k < i || k >= j || (k - i) % 2 == 1
        if s[k] != ' '
          outlist[c] = outlist[c] + 1
        end
      else
        if s[k] == ' '
          flg = false
        else
          inlist[c] = inlist[c] + 1
        end
      end
    end
    for k in 0..25 do
      if inlist[k] > 0 && outlist[k] > 0
        flg = false
      end
    end
    if flg
      puts 'Yes'
      exit()
    end
  end
end
rescue
end
puts 'NO'