n = int(input())
x = int(input())
a = int(input())
r = int(input())

overflow = 2**(n-1)


def deathturn(hp,damage):
    turn = hp // damage
    if hp % damage != 0:
        turn += 1
    return turn

print(min(deathturn(x,a),deathturn(overflow-x,r)))