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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;

using lint = long long;

lint layers[51];
lint putties[51];

lint P(int N, lint X){
    if(N == 0) return 1;
    if(X == 0 || X == 1) return 0;
    if(layers[N-1] + 1 >= X){
        return P(N-1, X-1);
    }
    else{
        return P(N-1, X - layers[N-1] - 2) + putties[N-1] + 1;
    }
}

int main(){
    int N;
    lint X;

    cin >> N >> X;
    layers[0] = 1;
    putties[0] = 1;
    for(int i=1;i<=N;i++){
        layers[i] = layers[i-1]*2 + 3;
        putties[i] = putties[i-1]*2 + 1;
    }
    cout << P(N, X) << endl;
    return 0;
}