def palindrome?(string)
  hash = {}

  string.each_char do |c|
    if hash[c] == nil
      hash[c] = 1
    else
      hash[c] += 1
    end
  end

  odd_chars = 0

  hash.each do |k,v|
    unless v % 2 == 0
      odd_chars += 1
      if odd_chars >= 2
        puts 'NO'
        return
      end
    end
  end

  puts 'YES'
end

string = $stdin.gets.chomp

palindrome?(string)