chrs = ("a".."z").to_a
array = Array.new(26, 0)
while true do
    str = gets.downcase
    break if str.count("a-z") == 0
    str = str.downcase
    chrs.each_with_index do |chr, index|
        array[index] += str.count(chr)
    end
end
chrs.each_with_index do |chr, index|
    puts chr + " : " + array[index].to_s
end