def main():
    N = int(input())
    X = int(input())
    A = int(input())
    B = int(input())
    attack = X // A if X % A == 0 else X // A + 1
    over = '0b' + '1' * 1 + '0' * (N-1)
    int_over = int(over, 0)
    heal = (int_over - X) // B if (int_over - X) % B == 0 else (int_over - X) // B + 1
    print(min(attack, heal))



if __name__ == "__main__":
    main()