#include <iostream>
#define int long long
using namespace std;
const int N = 1010, mod = 1e9 + 7;
int n, m, f[N][N];
signed main() {
    cin >> n >> m;
    f[0][0] = 1;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            f[i][j] = (f[i - 1][j - 1] + j * f[i - 1][j]) % mod;
    cout << f[n][m] << endl;
    return 0;
}