cal = (1..31).map { |i| i }
sum_day = cal.map do |d|
  if d < 10
    d
  elsif d >= 10
    d / 10 + d % 10
  end
end

sum_day1 = sum_day.dup
sum_day2 = sum_day.dup
sum_day3 = sum_day.dup

sum_day2.delete_at(30)
sum_day3.slice!(28, 3)

count = 0
(1..12).each do |x|
  case x
  when 1, 3, 5, 7, 8, 10, 11, 12
    y = sum_day1.select { |n| n == x }
    count += y.length
  when 4, 6, 9
    y = sum_day2.select { |n| n == x }
    count += y.length
  when 2
    y = sum_day3.select { |n| n == x }
    count += y.length
  end
end

puts count