#include <cmath>
#include <vector>
#include <map>
#include <functional>
#include <queue>
#include <iostream>
#include <string>
#include <iomanip>
#include <algorithm>
#include <functional>

using namespace std;

#define ll long long int
#define ti4 tuple<int,int,int,int>
#define pii pair<ll,ll>

int main()
{
    int n,k;
    cin >> n >> k;
    ll count = 0;
    for(ll i = 1;i < 1 << n;i++)
    {
        vector<int> l;
        vector<int> r;
        for(int j = 0;j < n;j++)
        {
            if(i & (1 << j))
            {
                l.push_back(j);
            }
            else
            {
                r.push_back(j);
            }
        }
        if(l[0] + 1 == k)
        {
            if(r.size() > 0)
            {
                if(l[l.size()-1] > r[0])
                {
                    count++;
                }
            }
        }
    }
    cout << count << endl;
    return 0;
}