// Why am I so dumb? :c
// chrono::system_clock::now().time_since_epoch().count()
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int MAXN = (int)3e3 + 5;
const int MOD = (int)1e9 + 7;
int dp[MAXN][MAXN];
int n, k;
int addMod(int a, int b, int m = MOD) {
a += b;
if (m <= a) {
a -= m;
}
return a;
}
int mulMod(int a, int b, int m = MOD) {
return a * 1ll * b % m;
}
void solve() {
scanf("%d %d", &n, &k);
dp[1][0] = 1;
for (int i = 1; i <= n; ++i) {
for (int j = 0; j < i; ++j) {
dp[i + 1][j] = addMod(dp[i + 1][j], mulMod(dp[i][j], j + 1));
dp[i + 1][j + 1] = addMod(dp[i + 1][j + 1], mulMod(dp[i][j], i - j));
}
}
printf("%d\n", dp[n][k - 1]);
}
int main() {
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
int tt = 1;
while (tt--) {
solve();
}
return 0;
}
