#include <cstdio>
#include <memory.h>
#define N 10001
#define P 10000

struct bigint{
    int sz;
    int a[777];
    bigint(int x=0){
        sz=0;
        memset(a,0,sizeof(a));
        while (x){
            a[++sz]=x%P;
            x/=P;
        }
        if (!sz) ++sz;
    }
    int & operator [] (int x){
        return a[x];
    }
    void print(){
        printf("%d",a[sz]);
        for (int i=sz-1;i>=1;i--) printf("%.4d",a[i]);
        printf("\n");
    }
} f[N],t(1);
int n,k;

bigint operator + (bigint & a,bigint & b){
    bigint res;
    int k=a.sz>b.sz?a.sz:b.sz;
    for (int i=1;i<=k;i++){
        res[i]+=a[i]+b[i];
        res[i+1]=res[i]/P;
        res[i]%=P;
    }
    if (res[k+1]) ++k;
    res.sz=k;
    return res;
}

bigint operator - (bigint &a,bigint &b){
        bigint res;
        int k=a.sz;
        for (int i=1;i<=k;i++){
            res[i]+=a[i]-b[i];
            if (res[i]<0){
                res[i]+=P;
                res[i+1]--;
            }
        }
        while (res[k]==0) --k;
        res.sz=k;
        return res;
}

int main(){
    scanf("%d%d",&n,&k);f[0]=bigint(1);
    if (k==0){
        printf("1\n");
        return 0;
    }
    for (int i=1;i<=n;i++){
        if (i<=k) f[i]=f[i-1]+f[i-1];
        else if (i==k+1){
            f[i]=f[i-1]+f[i-1];
            f[i]=f[i]-t;
        }
        else{
            f[i]=f[i-1]+f[i-1];
            f[i]=f[i]-f[i-k-2];
        }
    }
    f[n].print();
    return 0;
}