input = $stdin.readlines
input.map!{|a| a.chomp("\n").to_i}
input.count.times{|k|
  if input[k+1] == nil then
    print "Yay!"
    break
  end
  if input[k+1]-input[k] <= input[-1] then
    next
  else print ":("
    break
  end
    }