N = int(input())
X = int(input())
A = int(input())
B = int(input())

max_health = 2**(N -1) - 1

attack = 0
heal = 0

attack = int(X / A)
if X % A != 0:
	attack += 1

heal = int((max_health - X + 1) / B)
if (max_health - X + 1) % B != 0:
	heal += 1

if attack >= heal:
	print(heal)
else:
	print(attack)