//Create Time: 2018-05-09 20:51:48
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <cstdlib>
#include <sstream>
#include <fstream>
#include <functional>
#include <list>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cctype>
#include <ctime>
#include <utility>
#include <complex>
#include <cassert>
#include <climits>
#include <iterator>
#include <tuple>
using namespace std;
#define snuke(i,x) for (__typeof((x).begin()) i = (x).begin(); i != (x).end(); ++i)
#define rep(i,a,n) for (int i=(a);i<(n);i++)
#define per(i,n,a) for (int i=(n)-1;i>=(a);i--)
// #define OUT(x) std::cout<<(#x)<<":"<<(x)<<std::endl
// #define TST(x) std::cout<<(#x)<<":"<<(x)<<" "
#define OUT(args...) {string _s=#args;replace(_s.begin(),_s.end(),',',' ');stringstream _ss(_s);istream_iterator<string> _it(_ss);OUT_TST("\n",_it,args);}
#define TST(args...) {string _s=#args;replace(_s.begin(),_s.end(),',',' ');stringstream _ss(_s);istream_iterator<string> _it(_ss);OUT_TST("",_it,args);}
#define SZ(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define unq(x) sort(all(x)),(x).erase(unique(all(x)),(x).end())
#define mem(f,x) memset((f), (x), sizeof(f))
#define clr(f) mem(f,0)
#define x first
#define y second
#define mp make_pair
#define pb push_back
#define mt make_tuple
#define eb emplace_back
#define DEBUG
void OUT_TST(string s,istream_iterator<string> it) {cerr<<s;}
template<typename T, typename... Args> void OUT_TST(string s,istream_iterator<string> it,T a,Args... args){cerr<<*it<<"="<<a<<" ";OUT_TST(s,++it,args...);}
template<class T> void rd(T&ret){ret=0;bool ok=0,u=0;for(;;){int c=getchar();if(c>='0'&&c<='9')ret=(ret<<3)+(ret<<1)+c-'0',ok=1;else if(c=='-')u=1;else if(ok){if(u)ret*=-1;return;}}}
long long powmod(long long p,long long n,long long mod){long long ret=1;for(;n;n>>=1){if(n&1)ret=ret*p%mod;p=p*p%mod;}return ret;}
template <class T> bool chmin(T& a, const T &b) {return b < a? a = b, 1: 0;}
template <class T> bool chmax(T& a, const T &b) {return b > a? a = b, 1: 0;}
int gcd(int a,int b){return b?gcd(b,a%b):a;}
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii > vii;
typedef tuple<int,int,int> tp;
/****head****/
const int N=2005;
const ll mod=(ll)1e9+7;
template<int sz> struct Comb{
    const long long mod = ::mod;
    long long *fac, *ifac, *inv;
    long long mem_fac[sz+5],mem_ifac[sz+5],mem_inv[sz+5];

    // long long powmod(long long p,long long n,long long mod){long long ret=1;for(;n;n>>=1){if(n&1)ret=ret*p%mod;p=p*p%mod;}return ret;}

    Comb(long long *fa=0,long long *ifa=0,long long *iv=0){
        fac=fa?fa:mem_fac;
        ifac=ifa?ifa:mem_ifac;
        inv=iv?iv:mem_inv;
        fac[0]=fac[1]=1;
        ifac[0]=ifac[1]=1;
        inv[0]=inv[1]=1;  // set inv[0]=?
        for(int i=2;i<sz;++i){
            fac[i]=i*fac[i-1]%mod;
            inv[i]=(mod-mod/i)*inv[mod%i]%mod;
            ifac[i]=ifac[i-1]*inv[i]%mod;
        }
    }
    long long C(long long n,long long m){  // n >= m
        if(n<m)return 0;
        return (fac[n]*ifac[m]%mod)*ifac[n-m]%mod;
    }
    long long A(long long n,long long m){
        if(n<m)return 0;
        return fac[n]*ifac[n-m]%mod;
    }
};

// const int N=1<<17;
long long fac[N<<1],ifac[N<<1],inv[N<<1];
Comb<(N<<1)> comb(fac,ifac,inv);

int f[N][N],sum[N][N],n,K;
void add(int &a,int b){
    a+=b;if(a>=mod)a-=mod;
}
int main(){
    cin>>n>>K;
    if(K==1){
        cout<<powmod(2,max(n-2,0),mod)<<endl;
        return 0;
    }
    if(K==n){
        f[2][1]=1;
    } else{
        f[n-K+2][1]=1;
        rep(i,n-K+2,n+1){
            add(f[i][i-(n-K)-1],comb.C(i-2,n-K-1));
        }
    }
    sum[2][2]=f[2][2];
    sum[2][1]=sum[2][2];add(sum[2][1],f[2][1]);
    rep(i,3,n+1)per(j,i+1,1){
        add(f[i][j],sum[i-1][max(1,j-1)]);
        sum[i][j]=sum[i][j+1];
        add(sum[i][j],f[i][j]);
    }
    ll ans=0;
    rep(i,1,n+1)ans+=f[n][i];
    ans=ans%mod*powmod(2,max(n-K-1,0),mod)%mod;
    cout<<ans<<endl;
    return 0;
}


Measured memory_bytes: 30848