import math

def main():
    N = int(input())
    X = int(input())
    A = int(input())
    B = int(input())

    a = math.ceil(X/A)
    b = math.ceil(((2 ** (N-1)) - X) / B)

    if a > b:
        print(b)
    else:
        print(a)


if __name__ == '__main__':
    main()