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

def bitMAX(N):
    return 2**(N-1) -1

def bitMIN(N):
    return -1 * (2**(N-1))

def numATK():
    if X % A == 0:
        return X // A
    else:
        return (X // A) + 1

def numCURE():
    return (bitMAX(N) - X) // B + 1

atk = numATK()
cure = numCURE()
if atk > cure:
    print(cure)
else:
    print(atk)