#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>

#define REP(i,n) for(int (i)=0;(i)<(n);(i)++)
#define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define RREP(i,a) for(int (i)=(a)-1;(i)>=0;(i)--)
#define FORR(i,a,b) for(int (i)=(a)-1;(i)>=(b);(i)--)
#define PI acos(-1.0)
#define DEBUG(C) cout<<C<<endl;
#define VI vector<int>
#define VII vector<VI>
#define VL vector<LL>
#define VLL vector<VL>
#define VD vector<double>
#define VDD vector<VD>
#define PII pair<int,int>
#define PDD pair<double,double>
#define PLL pair<LL,LL>
#define VPII vector<PII>
#define ALL(a) (a).begin(),(a).end()
#define SORT(a) sort(ALL(a))
#define REVERSE(a) reverse(ALL(a))
#define MP make_pair
#define EP emplace_back
#define FORE(a,b) for(auto &&a:b)

using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
const int INF=1e9;
const int MOD=INF+7;

int N,K;
pair<set<int>,set<int>> f(int num){
    set<int> a,b;
    for(int i=0;i<N;i++){
        if(num&1) a.insert(i+1);
        else b.insert(i+1);
        num>>=1;
    }
    return MP(a,b);
}

int fact(int n){return (n?n*fact(n-1):1);}
int per(int n,int r){return (r?n*per(n-1,r-1):1);}
int comb(int n,int r){return per(n,r)/fact(r);}
int so(set<int> s){FORE(el,s){cout<<el<<" ";}cout<<endl;}

int main(void){
    cin>>N>>K;
    LL ans=0;
    for(int i=0;i<(1<<N);i++){
        auto sets=f(i);
        if(sets.first.size()==0 || sets.second.size()==0) continue;
        //if(sets.first.find(K)==sets.first.end()) continue;
        if(*sets.first.begin()!=K) continue;
        //so(sets.first);so(sets.second);
        ans++;
    }
    if(K==1) ans-=K;
    cout<<ans<<endl;
}