n,h,d,c=STDIN.read.split.map{|e| e.to_i}

h3=h
ans1=h3/d
h3=h3-ans1*d
while h3>0
	h3-=d
	ans1+=1
end

q=1<<(n-1)
h2=h
ans2=(q-h2)/c
h2=ans2*c+h2
while q>h2
	h2+=c
	ans2+=1
end
puts [ans1,ans2].min