Problem:
Score : 400 points

Problem Statement

In some other world, today is Christmas.

Mr. Takaha decides to make a multi-dimensional burger in his party. A level-L burger (L is an integer greater than or equal to 0) is the following thing:

A level-0 burger is a patty.

A level-L burger (L \geq 1) is a bun, a level-(L-1) burger, a patty, another level-(L-1) burger and another bun, stacked vertically in this order from the bottom.

For example, a level-1 burger and a level-2 burger look like BPPPB and BBPPPBPBPPPBB (rotated 90 degrees), where B and P stands for a bun and a patty.

The burger Mr. Takaha will make is a level-N burger. Lunlun the Dachshund will eat X layers from the bottom of this burger (a layer is a patty or a bun). How many patties will she eat?

Constraints

1 \leq N \leq 50

1 \leq X \leq ( the total number of layers in a level-N burger )

N and X are integers.

Input

Input is given from Standard Input in the following format:

N X

Output

Print the number of patties in the bottom-most X layers from the bottom of a level-N burger.

Sample Input 1

2 7

Sample Output 1

4

There are 4 patties in the bottom-most 7 layers of a level-2 burger (BBPPPBPBPPPBB).

Sample Input 2

1 1

Sample Output 2

0

The bottom-most layer of a level-1 burger is a bun.

Sample Input 3

50 4321098765432109

Sample Output 3

2160549382716056

A level-50 burger is rather thick, to the extent that the number of its layers does not fit into a 32-bit integer.

Solution in Python (3.4.3) (judge verdict: Wrong Answer)

N, X = map(int, input().split())

a = [1]
p = [1]
for i in range(N):
    a.append(a[-1]*2 + 3)
    p.append(p[-1]*2 + 1)
# print(a, p)

def f(lv, x):
    c = a[lv-1] + 2
    if x == 1:
        # print(f"1, {lv}, {x}")
        return 0
    elif 1 < x < c:
        # print(f"2, {lv}, {x}")
        return f(lv-1, x-1)
    elif x == c:
        # print(f"3, {lv}, {x}")
        return p[lv-1] + 1
    elif c < x < a[lv]:
        # print(f"4, {lv}, {x}")
        return p[lv-1] + 1 + f(lv-1, x-c)
    else:
        # print(f"5, {lv}, {x}")
        return p[lv]

print(f(N, X))