#include <bits/stdc++.h>
 #include <atcoder/all>
 
 
 
 
using namespace atcoder;
 
 
// tabaicho see https://boostjp.github.io/tips/multiprec-int.html   
 //#include <boost/multiprecision/cpp_int.hpp>
 
// using namespace boost::multiprecision;
 
// cpp_int
// int128_t
// int256_t
// int512_t
// int1024_t
 
// uint128_t
// uint256_t
// uint512_t
// uint1024_t
 
 
 
#define int long long
 #define inf  1000000007
// #define inf  998244353
 
 #define pa pair<int,int>
 #define ll long long
 #define PI 3.14159265358979323846
 #define  mp make_pair
 #define  pb push_back
 #define EPS (1e-8)
 
      using namespace std;
                                          
 int dx[8]={0,1,0,-1,1,1,-1,-1};
 int dy[8]={1,0,-1,0,-1,1,1,-1};
                                            
class pa3{
	public:
	int x;
	int y,z;
	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
	bool operator < (const pa3 &p) const{
		if(x!=p.x) return x<p.x;
		if(y!=p.y) return y<p.y;
		 return z<p.z;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator > (const pa3 &p) const{
		if(x!=p.x) return x>p.x;
		if(y!=p.y) return y>p.y;
		 return z>p.z;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa3 &p) const{
		return x==p.x && y==p.y && z==p.z;
	}
		bool operator != (const pa3 &p) const{
			return !( x==p.x && y==p.y && z==p.z);
	}
 
};
 
class pa4{
	public:
	int x;
	int y,z,w;
	pa4(int x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
	bool operator < (const pa4 &p) const{
		if(x!=p.x) return x<p.x;
		if(y!=p.y) return y<p.y;
		if(z!=p.z)return z<p.z;
		return w<p.w;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator > (const pa4 &p) const{
		if(x!=p.x) return x>p.x;
		if(y!=p.y) return y>p.y;
		if(z!=p.z)return z>p.z;
		return w>p.w;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa4 &p) const{
		return x==p.x && y==p.y && z==p.z &&w==p.w;
	}
		
 
};
class pa2{
	public:
	int x,y;
	pa2(int x=0,int y=0):x(x),y(y) {}
	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
	bool operator < (const pa2 &p) const{
		return y != p.y ? y<p.y: x<p.x;
	}
	bool operator > (const pa2 &p) const{
		return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa2 &p) const{
		return abs(x-p.x)==0 && abs(y-p.y)==0;
	}
	bool operator != (const pa2 &p) const{
		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
	}
		
 
};
 
 
 
string itos( int i ) {
	ostringstream s ;
	s << i ;
	return s.str() ;
}
 
int Gcd(int v,int b){
	if(v==0) return b;
	if(b==0) return v;
	if(v>b) return Gcd(b,v);
	if(v==b) return b;
	if(b%v==0) return v;
	return Gcd(v,b%v);
}
 
 
 
int extgcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    int d = extgcd(b, a%b, y, x);
    y -= a/b * x;
    return d;
}
pa operator+(const pa & l,const pa & r) {   
    return {l.first+r.first,l.second+r.second};                                    
}    
pa operator-(const pa & l,const pa & r) {   
    return {l.first-r.first,l.second-r.second};                                    
}  
 
ostream& operator<<(ostream& os, const vector<int>& VEC){
	for(auto v:VEC)os<<v<<" ";
    return os;
}
 
 
 
ostream& operator<<(ostream& os, const pa& PAI){
	os<<PAI.first<<" : "<<PAI.second;
    return os;
}
 
ostream& operator<<(ostream& os, const pa3& PAI){
	os<<PAI.x<<" : "<<PAI.y<<" : "<<PAI.z;
    return os;
}
 
ostream& operator<<(ostream& os, const pa4& PAI){
	os<<PAI.x<<" : "<<PAI.y<<" : "<<PAI.z<<" : "<<PAI.w;
    return os;
}
 
ostream& operator<<(ostream& os, const vector<pa>& VEC){
	for(auto v:VEC)os<<v<<" ";
    return os;
}
 
 
ostream& operator<<(ostream& os, const vector<pa3>& VEC){
	for(auto v:VEC){
		os<<v<<" ";
	os<<endl;
	}
    return os;
}
 
int beki(int wa,ll rr,int warukazu){
	if(rr==0) return 1%warukazu;
	if(rr==1) return wa%warukazu;
	wa%=warukazu;
	if(rr%2==1) return ((ll)beki(wa,rr-1,warukazu)*(ll)wa)%warukazu;
	ll zx=beki(wa,rr/2,warukazu);
	return (zx*zx)%warukazu;
}
 
              
int pr[2521000];
int inv[2521000];
 
 
 
 
const int mod=1000000007;
 
int comb(int nn,int rr){
	if(nn==-1&&rr==-1)return 1;
	if(rr<0 || rr>nn || nn<0) return 0;
	int r=pr[nn]*inv[rr];
	r%=mod;
	r*=inv[nn-rr];
	r%=mod;
	return r;
}
 
void gya(int ert){
	pr[0]=1;
	for(int i=1;i<=ert;i++){
		pr[i]=((ll)pr[i-1]*i)%mod;
	}
		inv[ert]=beki(pr[ert],mod-2,mod);
	for(int i=ert-1;i>=0;i--){
		inv[i]=(ll)inv[i+1]*(i+1)%mod;
	}
}
 
 
                
 
 
                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
//    mt19937(clock_per_sec);
  //  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;

int beki2(int wa,ll rr){
	if(rr==0) return 1;
	if(rr==1) return wa;
	//wa%=warukazu;
	if(rr%2==1) return ((ll)beki2(wa,rr-1)*(ll)wa)%mod;
	ll zx=beki2(wa,rr/2);
	return (zx*zx)%mod;
}

int beki3(int a,int b){
	int ANS=1;
	int be=a%mod;
	while(b){
		if(b&1){
			ANS*=be;
			ANS%=mod;
		}
		be*=be;
		be%=mod;
		b/=2;
	}
	return ANS;
}





int dp[110][3]={};

vector<int>co;

int han(int l,int r){
	int n=co.size();
	n--;
		r=min(r,n);
	l=max(0ll,l);
	if(l>r)return 0;

	if(l)return (co[r]+mod-co[l-1])%mod;
	return co[r];
}

void solve(){

	gya(1000020);
	int n,m;
	cin>>n>>m;
	
	for(int i=0;i<=n;i++)co.pb(comb(n,i));
	for(int i=1;i<=n;i++)co[i]=(co[i-1]+co[i])%mod;
	int ans=0;
	for(int i=1;i<=n-m;i++){
		//[m,n-i]
		ans+=han(m,(n-i)/2);

		int p=(n-i)/2+1;
		p=max(p,m);
		int q=n-p;
		ans+=han(-i,q-i);
		
		//cout<<" "<<ans<<endl;
		//ans+=han(0,n-i-m);
		ans%=mod;
	}
	//cout<<ans<<endl;
	for(int i=1;i<=n;i++){
		ans+=han(0,min((n-i)/2,n-m));
		
		int p=(n-i)/2+1;
		
		if(p<=n-m){
			int q=n-p;
			ans+=han(m-i,q-i);
	//		cout<<"! "<<han(m-i,q-i)<<endl;
		}
	//	cout<<" "<<ans<<endl;
		ans%=mod;
	}
//	cout<<ans<<endl;
	ans+=han(m,n)*n%mod;
	ans%=mod;
	cout<<ans<<endl;
	
	
}


signed main(){
 
	//mod=inf;
	cin.tie(0);
	ios::sync_with_stdio(false);


	int n=1;
	//cin>>n;
	for(int i=0;i<n;i++)solve();
	
 
	return 0;
	
}