#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template <class A, class B>
bool maximize(A &a, const B b) {
if (a < b) {
a = b;
return true;
} return false;
}
template <class A, class B>
bool minimize(A &a, const B b) {
if(a > b) {
a = b;
return true;
} return false;
}
using pII = pair <int, int>;
using vI = vector <int>;
using vL = vector <long long>;
using pLI = pair <long long, int>;
#define BIT(mask, i) ((mask >> (i)) & 1)
#define MASK(a) (1LL<<(a))
#define FOR(i, a, b) for(int i = a; i <= (int)b; i++)
#define FORD(i, a, b) for(int i = a; i >= (int)b; i--)
#define fi first
#define se second
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) (int)a.size()
const int mod = 1e9 + 7;
const int maxn = 2e5 + 5;
void add (int &x, const int y) {
x+= y;
if (x >= mod) x-= mod;
}
int n, k;
int fact[maxn], inv_fact[maxn];
int iPow (int x, int y) {
if (y == 0) return 1;
if (y == 1) return x;
int c = iPow (x, y / 2);
if (y & 1) return 1LL * c * c % mod * x % mod;
else return 1LL * c * c % mod;
}
int C (int n, int k) {
if (k > n) return 0;
return 1LL * fact[n] * inv_fact[k] % mod * inv_fact[n - k] % mod;
}
namespace sub1 {
int a[15];
void solve () {
FOR(i, 1, n) a[i] = i;
int ans = 0;
do {
int cnt = 0;
vector <int> dd(n + 2, 0);
FOR(i, 1, n) {
if (dd[a[i]] == 0) {
cnt++;
int last = - 1;
FOR(j, i, n) if (!dd[a[j]] && a[j] >= last) {
dd[a[j]] = 1;
last = a[j];
} else break;
}
}
if (cnt == k) ans++;
} while (next_permutation(a + 1, a + 1 + n));
cout << ans;
}
}
namespace sub23 {
int dp[3005][3005];
void solve () {
dp[1][1] = 1;
FOR(i, 1, n) FOR(j, 1, k) {
/// create new group
if (j < k) {
add(dp[i + 1][j + 1], dp[i][j]);
add(dp[i + 1][j + 1], 1LL * dp[i][j] * (i - j) % mod);
}
/// join group
add (dp[i + 1][j], 1LL * dp[i][j] * j % mod);
}
cout << dp[n][k];
}
}
void process () {
cin >> n >> k;
if (n <= 10) {
return sub1::solve();
}
if (n <= 3000) {
return sub23::solve();
}
}
int main () {
ios_base::sync_with_stdio(0);
cin.tie(0);
#define taskname "kieuoanh"
if (fopen(taskname".inp", "r")) {
freopen(taskname".inp", "r", stdin);
freopen(taskname".out", "w", stdout);
}
fact[0] = 1;
FOR(i, 1, maxn - 5) fact[i] = 1LL * fact[i - 1] * i % mod;
inv_fact[maxn - 5] = iPow(fact[maxn - 5], mod - 2);
FORD(i, maxn - 6, 0) inv_fact[i] = 1LL * inv_fact[i + 1] * (i + 1) % mod;
int tc = 1; /// cin >> tc;
while (tc--) process();
return 0;
}
