attrs = Array.new
while line = $stdin.gets
    attrs << line.chomp.split.map{|v| v.to_i }
end

attrs.flatten!
k = attrs.pop
ng = 0
for i in 0..(attrs.length - 1) do
  for j in 0..(attrs.length - 1) do
    if i == j then
      next
    end
    if (attrs[i] - attrs[j]).abs > k then
      ng = 1
    end
  end
end

if ng == 0 then
  puts "Yay!"
else
  puts ":("
end