
input = readlines
input.each{|num|
    num = num.chomp!
}


i = 0
stat = "0"

while i < (input.length-1)
    j = i + 1
    while j < (input.length-1) 

        dis = input[j].to_i - input[i].to_i

        if dis > input[input.length].to_i
            stat = ":("
        elsif stat != ":("
            stat = "Yay!"
        end
    
        j = j + 1
    end
    
    i = i + 1
end

print stat