ant= []
while a = gets do
    ant.push(a)
end

k = ant.last.to_i
ant.delete_at(ant.length-1)

connect = "Yay!"
last = ant[0].to_i
ant.each do |a|
    distance = a.to_i - last.to_i
    if distance.to_i > k
        connect = ":("
    end
end

puts connect