# HINT
# 以下のようにすると任意の年月日の範囲の日付を取得できる
require "date"
days = (Date.parse("2015/01/01")..Date.parse("2015/12/31")).to_a
# pp days
# => [#<Date: 2020-01-01 ((2458850j,0s,0n),+0s,2299161j)>,
#     #<Date: 2020-01-02 ((2458851j,0s,0n),+0s,2299161j)>,
#     #<Date: 2020-01-03 ((2458852j,0s,0n),+0s,2299161j)>,
#     #<Date: 2020-01-04 ((2458853j,0s,0n),+0s,2299161j)>]

count = 0
days.each do |day|
    if day.month == day.day.to_s.chars.map(&:to_i).sum
        count += 1
    end
end

puts count