#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
bool be;
constexpr int N = 5005, mod = 1e9 + 7;
int n, k, f[N][N], sum[N][N];
bool en;
int main()
{
#ifdef IAKIOI
	freopen("in.in", "r", stdin);
//	freopen("out.out", "w", stdout);
	cerr << (&be - &en) / 1024.0 / 1024 << " MB\n-------------------\n";
#endif
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin >> n >> k;
	f[2][n - 1] = 1;
	for (int i = n - 1; i >= 1; i -= 2) sum[2][i] = 1;
	int ans = 2 * (k - 1);
	for (int i = 3; i <= min(n, k); ++i) {
		for (int j = n - i + 1; j >= 1; --j) {
			f[i][j] = (sum[i - 1][j + 1] + sum[i - 1][i + j - 1]) % mod;
			ans = (ans + (ll) (f[i][j] * 2) * (k - i + 1)) % mod;
			sum[i][j] = (sum[i][j + 2] + f[i][j]) % mod;
		}
	}
	cout << ans << endl;
	return 0;
}