#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcount
#define ll long long
#define mp make_pair
#define f first
#define s second
const int N = 3001, MOD = 1000 * 1000 * 1000 + 7;
int n, k, dp[N][N];
void add(int &a, int b) {
a += b; a %= MOD;
}
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
cin >> n >> k;
--k;
dp[1][0] = 1;
for (int i = 1; i < n; ++i) {
for (int j = 0; j <= k; ++j) {
add(dp[i + 1][j], dp[i][j] * (j + 1));
add(dp[i + 1][j + 1], dp[i][j] * (i - j));
}
}
cout << dp[n][k] << '\n';
}
