euler_19.re

# Reia script

module Sundays
  def first_day_is_sunday(y, m)
    calendar::day_of_the_week(y, m, 1) == 7
  end
  
  def count_valid_months
    [ 1 | y in 1901..2000, m in 1..12, first_day_is_sunday(y,m) ].size()
  end
end

puts(Sundays.count_valid_months()) # => 171