if __name__ == "__main__":
	N = int(input())
	X = int(input())
	A = int(input())
	B = int(input())

	overval = 2 ** (N-1)
	if X % A ==0:
		attack = X//A
	else:
		attack = X//A + 1
	if (overval-X) % B == 0:
		heal = (overval-X) //B
	else:
		heal = (overval-X) //B + 1
		
	print(min([attack,heal]))