#ifdef ONPC
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#define char unsigned char
#define rep(i, a, b) for(int i=a; i< (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define pb push_back
#define LSOne(S) ((S) & -(S))
using namespace std;
// mt19937 rnd(239);
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> int sgn(T x) { return (T(0) < x) - (x < T(0)); }
typedef long double T;
typedef complex<T> pt;
#define X real()
#define Y imag()
template<class T>
istream& operator>> (istream& is, complex<T>& p) {
T value;
is >> value;
p.real(value);
is >> value;
p.imag(value);
return is;
}
typedef long long ll;
typedef long double ld;
using pi = pair<ll, ll>;
using vi = vector<ll>;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;
int popcnt(int x) { return __builtin_popcount(x); }
int popcnt(ll x) { return __builtin_popcountll(x); }
#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
#define LB(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define UB(c, x) distance((c).begin(), upper_bound(all(c), (x)))
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef DEBUG
#define dbg(x...) cerr << "\e[91m"<<__func__<<":"<<__LINE__<<" [" << #x << "] = ["; _print(x); cerr << "\e[39m" << endl;
#else
#define dbg(x...)
#endif
template<typename S, typename T = S> void chmin(S &s, T t) {s = s < t ? s : t;}
template<typename S, typename T = S> void chmax(S &s, T t) {s = s > t ? s : t;}
const int INF = 1e9; // 10^9 = 1B is < 2^31-1
const ll LLINF = 4e18; // 4*10^18 is < 2^63-1
const double EPS = 1e-9;
const ll MOD = 1e9+7;
ll N, K;
ll dp1[5050][5050], dp2[5050][5050];
struct Fenwick {
vector<ll> tree;
int n;
Fenwick(int n=5050) : n(n) {
tree.assign(n, 0);
}
void point_add(int pos, ll val) {
for (; pos < n; pos |= (pos + 1)) {
tree[pos] += val;
}
}
ll find_sum(int r) { // [0, r]
ll ans = 0;
for (; r >= 0; r = (r & (r + 1)) - 1) {
ans += tree[r];
ans%=MOD;
}
return ans;
}
ll find_sum(int l, int r) { // [l, r)
if(l>=r) return 0;
return find_sum(r - 1) - find_sum(l - 1);
}
};
//Fenwick ft[5050];
vector<Fenwick> ft1, ft2;
ll rec(int n, int a1, bool inc) {
if(inc) {
if(dp1[n][a1]!=-1) return dp1[n][a1];
dp1[n][a1]=0;
//std::cout << "from " << n << " " << a1 << "|"<< (inc) << " " << a1+1 << " to " << n-a1 << " with " << n-a1 << std::endl;
std::cout << "dec: "<< a1+1 << " " << n-a1+1 << std::endl;
dp1[n][a1]=ft2[n-a1].find_sum(a1+1, n-a1+1);
if(false)
for (int i = a1+1; i <= n-a1; i++) {
dp1[n][a1]+= rec(n-a1, i, false);
dp1[n][a1]%=MOD;
}
//std::cout << n << " " << a1 << " " << (inc) << ": " << dp1[n][a1] << std::endl;
ft1[n].point_add(a1, dp1[n][a1]);
return dp1[n][a1];
} else {
if(dp2[n][a1]!=-1) return dp2[n][a1];
dp2[n][a1]=0;
//std::cout << 1 << " to " << a1-1 << " with " << n-a1 << std::endl;
std::cout << "inc: " << 1 << " " << min(a1, n-a1)+1 << std::endl;
dp2[n][a1]=ft1[n-a1].find_sum(1, min(a1, n-a1));
if(false)
for (int i = 1; i < min(a1, n-a1); i++) {
if(i<=n-a1) {
//std::cout << "from " << n << " " << a1 << "|"<< (inc) << " " << 1 << " to " << a1-2 << " with " << n-a1 << std::endl;
dp2[n][a1]+=rec(n-a1, i, true);
dp2[n][a1]%=MOD;
}
}
ft2[n].point_add(a1, dp2[n][a1]);
//std::cout << n << " " << a1 << " " << (inc) << ": " << dp2[n][a1] << std::endl;
return dp2[n][a1];
}
}
int solve() {
std::cin >> N >> K;
ft1.resize(5050);
ft2.resize(5050);
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
if(i==j) {
ft1[i].point_add(j, 1);
ft2[i].point_add(j, 1);
} else if(i+1==j) {
ft1[i].point_add(j, 1);
ft2[i].point_add(j, 1);
}
}
}
//rec(N, K, true);
//rec(N, K, false);
for (int n = 1; n <= N; n++) {
for (int a1 = 1; a1 <= n; a1++) {
// inc
//std::cout << "INC: " << n << ", " << a1 << " " << a1+1 << " to " << n-a1+1 << std::endl;
//dp1[n][a1]=ft2[n-a1].find_sum(a1+1, n-a1+1);
// dec
//std::cout << "DEC: " << n << ", " << a1 << " " << 1 << " to " << min(a1, n-a1)+1 << std::endl;
//dp2[n][a1]=ft1[n-a1].find_sum(1, min(a1, n-a1)+1);
ft1[n].point_add(a1, ft2[n-a1].find_sum(a1+1, n-a1+1));
ft2[n].point_add(a1, ft1[n-a1].find_sum(1, min(a1, n-a1)+1));
}
}
/*
for (int n = 1; n <= N; n++) {
for (int k = 1; k <= n; k++) {
//std::cout << n << " " << k << std::endl;
std::cout << k+1 << " " << n-k-1 << std::endl;
for (int l = k+1; l < n-k; l++) {
std::cout << "["<<n <<","<<k <<"]" << ": " << n-k << " " << l << std::endl;
dp[n][k]+=dp[n-k][l];
}
}
}
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= K; j++) {
std::cout << dp[i][j] << " ";
}
std::cout << std::endl;
}
*/
if(N==K) {
std::cout << 1 << std::endl;
return 0;
}
std::cout << (ft1[N].find_sum(K, K+1)+ft2[N].find_sum(K, K+1))%MOD << std::endl;
return 0;
}
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
int TET = 1;
//cin >> TET;
for (int i = 1; i <= TET; i++) {
#ifdef ONPC
cout << "TEST CASE#" << i << endl;
#endif
if (solve()) {
break;
}
#ifdef ONPC
cout << "__________________________" << endl;
#endif
}
#ifdef ONPC
cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
#endif
}
