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: Accepted)

# -*- coding: utf-8 -*-
"""
Created on Sun May 19 16:57:17 2019

@author: Yamazaki Kenichi
"""

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

dp = [[1,1] for i in range(N+1)]
for i in range(1,N+1):
    dp[i][0] = dp[i-1][0]*2 + 1
    dp[i][1] = dp[i-1][1]*2 + 3

ans = 0
for i in range(2,N+2):
    if X - (dp[-i][1] + 2) >= 0:
        ans += dp[-i][0] + 1
        X -= (dp[-i][1] + 2)
#        print(ans,X,dp[-i])
    else:
        X -= 1
#        print(ans,X,dp[-i])
    if i == N+1 and X >= 1:
        ans += 1
#        print(ans,X,dp[-i])
print(ans)