antennas = Array.new(5) do
  gets.chomp.to_i
end
k = gets.chomp.to_i

max_diff = antennas
         .combination(2)
         .map{|x, y| (x - y).abs }
         .sort
         .max

if max_diff >= k
  puts ':('
else
  puts 'Yay!'
end