#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<unordered_map>
#include<array>
#include<map>
#include<bitset>
#include<iomanip>
#include<list>
#include <numeric>
using namespace std;
typedef unsigned long long int ulint;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
#define RE return 0
//ios::sync_with_stdio(false);
//std::cin.tie(0);
//<< setprecision(20)
const int mod=(int)1e9+7;

const llint big=(llint)(2.19e18+1);
const long double pai=3.141592653589793238462643383279502884197;
const long double ena=2.71828182845904523536;
const long double eps=1e-7;
template <class T,class U>bool mineq(T& a,U b){if(a>b){a=b;return true;}return false;}
template <class T,class U>bool maxeq(T& a,U b){if(a<b){a=b;return true;}return false;}
template <class T> void soun(T& ar)
{sort(ar.begin(),ar.end());ar.erase(unique(ar.begin(),ar.end()),ar.end());}
llint gcd(llint a,llint b){if(a%b==0){return b;}else{return gcd(b,a%b);}}
llint lcm(llint a,llint b){return a/gcd(a,b) *b;}
template<class T,class U> auto LB(T& ve,U in){return lower_bound(ve.begin(),ve.end(),in);}
template<class T,class U> auto UB(T& ve,U in){return upper_bound(ve.begin(),ve.end(),in);}
template<class T,class U> auto LBI(T& ve,U in){return LB(ve,in)-ve.begin();}
template<class T,class U> auto UBI(T& ve,U in){return UB(ve,in)-ve.begin();}
template<class T> void SO(T& ve){sort(ve.begin(),ve.end());}
template<class T> void REV(T& ve){reverse(ve.begin(),ve.end());}

template <uint64_t MOD_ = 1000000007>
class mint_base
{
public:
	static constexpr auto MOD = MOD_;
	static_assert(!(MOD <= 2), "MOD cannot be below 2.");
	static_assert(MOD <= (0xFFFFFFFFFFFFFFFF / 2), "MOD is too big");//加算してオーバーフローしない
	static_assert(MOD <= 0xFFFFFFFF, "MOD is too big");//乗算してオーバーフローしない
	constexpr mint_base<MOD> operator+(const mint_base<MOD> &other)const noexcept
	{auto v = *this;return v += other;}
	constexpr mint_base<MOD> operator-(const mint_base<MOD> &other)const noexcept
	{auto v = *this;return v -= other;}
	constexpr mint_base<MOD> operator*(const mint_base<MOD> &other)const noexcept
	{auto v = *this;return v *= other;}
	constexpr mint_base<MOD>& operator+=(const mint_base<MOD> &other) noexcept
	{a += other.a;if (MOD <= a) { a -= MOD; };return *this;}
	constexpr mint_base<MOD>& operator-=(const mint_base<MOD> &other) noexcept
	{if (a >= other.a) {a -= other.a;}else {a = (a + MOD) - other.a;}return *this;}
	constexpr mint_base<MOD>& operator*=(const mint_base<MOD> &other) noexcept
	{a *= other.a;a %= MOD;return *this;}
	constexpr mint_base<MOD> operator+()const noexcept { return *this; }
	constexpr mint_base<MOD> operator-()const noexcept
	{return{ MOD - a, mod_value_tag{} };}
	constexpr mint_base<MOD>& operator++() noexcept
	{if (MOD <= ++a) { a = 0; };return *this;}
	constexpr mint_base<MOD>& operator--() noexcept
	{if (a <= 0) { a = MOD; };--a;return *this;}
	constexpr mint_base<MOD> operator++(int) noexcept
	{auto tmp = *this;++*this;return tmp;}
	constexpr mint_base<MOD> operator--(int) noexcept
	{auto tmp = *this;--*this;return tmp;}
	constexpr mint_base<MOD>& operator=(const mint_base<MOD> &other) noexcept
	{a = other.a;return *this;}
	constexpr operator uint64_t()const noexcept
	{return a;}
	constexpr explicit operator unsigned()const noexcept
	{return (unsigned)a;}
	static constexpr uint64_t getmod() noexcept
	{return MOD;}
	constexpr mint_base(uint64_t a_) noexcept :a(a_ % MOD) {}
	constexpr mint_base()noexcept : a(0) {}
	struct mod_value_tag {};
	constexpr mint_base(uint64_t a_, mod_value_tag) :a(a_) {}
private:
	uint64_t a;
};
//mint_base型のstreamへの出力
template<uint64_t MOD> std::ostream& operator<<(std::ostream& os, mint_base<MOD> i)
{os << (uint64_t)i;return os;}
//mint_base型のstreamからの入力
template<uint64_t MOD> std::istream& operator >> (std::istream& is, mint_base<MOD>& i)
{uint64_t tmp;is >> tmp;i = tmp;return is;}

int main(void){
	int A,B,i,j;cin>>A>>B;
	//nCrを高速に求めることもできるが、どうせ累積和するのでパスカルの三角形する
	static mint_base<> nCr[2011][4011];//r,b-r+2005
	static mint_base<> wa[2011][4011];
	nCr[0][2005]=1;
	for(i=0;i<2010;i++){
		for(j=2005;j<4010;j++){
			nCr[i+1][j]+=nCr[i][j];
			nCr[i][j+1]+=nCr[i][j];
		}
	}
	for(i=0;i<2010;i++){
		for(j=2005;j<4010;j++){
			wa[i][j]=nCr[i][j];
		}
	}
	//累積和を二回とってアを求める
	for(i=2005;i<=4010;i++){
		for(j=0;j<2005;j++){
			wa[j+1][i-j-1]+=wa[j][i-j];
		}
	}
	for(i=2005;i<=4010;i++){
		for(j=0;j<2005;j++){
			wa[j+1][i-j-1]+=wa[j][i-j];
		}
	}
	mint_base<> ans=0;
	//cerr<<"de"<<wa[2][2005+3-2]<<endl;
	//cerr<<"de"<<wa[0][2004]<<endl;
	for(int r=0;r<=A;r++){//最初にbが出るまでにrをとらなった数
		//ここでbをとる
		for(int b=max(1,B-r);b<=B;b++){
			//if(B-r>b){continue;}
			//合計B個とるけど最初は青
			//そのうち青をb個とる 残りはB-b個
			//赤をB-bことる 残りはr-B+b個
			//   自由青取る,赤とる   残りの赤,残りの青-赤-1
			ans+=nCr[b-1][B-b+2005]*wa[r-B+b][2005+B-b-r+B-b-1];
			//cerr<<"de "<<b-1<<" "<<B-b<<" "<<r-B+b<<" "<<B-b-r+B-b-1<<endl;
		}
		ans++;//b=0
	}
	cout<<ans<<endl;
	return 0;
}

Measured memory_bytes: 125184