#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=1167167167167167167;
const int INF=2100000000;
ll mod=1e9+7;
#define rep(i,a) for (ll i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}


namespace po167{
struct combination{
	std::vector<long long> fact;
	std::vector<long long> rev;
	std::vector<long long> fact_rev;
	long long MOD;
	combination(int max,long long mod):MOD(mod),fact(max+1),rev(max+1),fact_rev(max+1){
		for(long long i=0;i<=max;i++){
			if(i<2){
				fact[i]=1;
				fact_rev[i]=1;
				rev[i]=1;
				continue;
			}
			fact[i]=(fact[i-1]*i)%mod;
			rev[i]=mod-((mod/i)*rev[mod%i])%mod;
			fact_rev[i]=(fact_rev[i-1]*rev[i])%mod;
		}
	}
	long long Comb(int x,int y){
		if(x==y) return 1;
		if (x<y||y<0) return 0;
		return (((fact_rev[y]*fact_rev[x-y])%MOD)*fact[x])%MOD;
	}
};
}
using po167::combination;


//  rainy ~ 雨に打たれて ~
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	ll N,M;
	cin>>N>>M;
	combination table(1e6+1e4,mod);
	ll ans=0;
	for(int i=M;i<=N;i++){
		ans+=(2*i)*table.Comb(N,i);
		ans%=mod;
	}
	vector<ll> sum(N+2);
	rep(i,N+1){
		sum[i+1]=sum[i];
		sum[i+1]=(sum[1+i]+table.Comb(N,i))%mod;
	}
	for(ll i=0;i<=N-M;i++){
		ans+=2*sum[min(i,N-i)];
		ans%=mod;
		ans+=(2*max(0ll,2*i-N)*table.Comb(N,i))%mod;
		ans%=mod;
	}
	cout<<ans%mod<<"\n";
}