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

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

attack = 0
heal = 0

HP = X
while HP > 0:
	HP -= A
	attack += 1

HP = X
while HP <= max_health:
	HP += B
	heal += 1

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