#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define F first
#define S second
#define debug(x) cerr<<#x<<" :"<<x<<"\n"
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define FAST ios_base::sync_with_stdio(false), cin.tie(), cout.tie();
#define int long long
typedef long long ll;
typedef long double ld;
const int maxn = 5e5 + 7;
const int mod = 1e9 + 7;
const int INF = 1e9 + 7;
const int mlog = 20;
const int SQ = 400;
int fact[maxn];
int pw(int a,int b)
{
int res = 1;
while(b)
{
if(b & 1) res = res * a % mod;
a = a*a % mod;
b/= 2;
}
return res;
}
int C(int n,int r) { return fact[n] * (pw(fact[r] * fact[n - r] % mod, mod-2)) % mod; }
int32_t main()
{
FAST;
fact[0] = 1;
for(int i = 1; i < maxn; i++) fact[i] = fact[i - 1] * i % mod;
int n, k;
cin >> n >> k;
int ans = 0;
for(int i = 0; i <= k - 1; i++)
for(int j = 0; j <= k - i - 1; j++)
{
int res = (pw(k - i - j, n) * C(n - k + j, j) % mod * C(k - j, i) % mod);
if((i + j) % 2 == 1) res *= -1;
ans = (ans + res) %mod;
}
ans = (ans + mod) % mod;
cout << ans << "\n";
return 0;
}
