#include <bits/stdc++.h>
#define MP make_pair
#define PB push_back
#define int long long
#define st first
#define nd second
#define rd third
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define __builtin_ctz __builtin_ctzll
#define __builtin_clz __builtin_clzll
#define __builtin_popcount __builtin_popcountll
using namespace std;
template<typename TH> void _dbg(const char* sdbg, TH h) { cerr<<sdbg<<"="<<h<<"\n"; }
template<typename TH, typename... TA> void _dbg(const char* sdbg, TH h, TA... t) {
  while(*sdbg != ',') { cerr<<*sdbg++; } cerr<<"="<<h<<","; _dbg(sdbg+1, t...);
}
#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<"\n"; }}
#else
#define debug(...) (__VA_ARGS__)
#define debugv(x)
#define cerr if(0)cout
#endif
#define next ____next
#define prev ____prev
#define left ____left
#define hash ____hash
typedef long long ll;
typedef long double LD;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<pair<int, int> > VPII;
typedef vector<pair<ll, ll> > VPLL;

template<class C> void mini(C&a4, C b4){a4=min(a4, b4); }
template<class C> void maxi(C&a4, C b4){a4=max(a4, b4); }
template<class T1, class T2>
ostream& operator<< (ostream &out, pair<T1, T2> pair) { return out << "(" << pair.first << ", " << pair.second << ")";}
template<class A, class B, class C> struct Triple { A first; B second; C third;
  bool operator<(const Triple& t) const { if (st != t.st) return st < t.st; if (nd != t.nd) return nd < t.nd; return rd < t.rd; } };
template<class T> void ResizeVec(T&, vector<int>) {}
template<class T> void ResizeVec(vector<T>& vec, vector<int> sz) {
  vec.resize(sz[0]); sz.erase(sz.begin()); if (sz.empty()) { return; }
  for (T& v : vec) { ResizeVec(v, sz); }
}
typedef Triple<int, int, int> TIII;
template<class A, class B, class C>
ostream& operator<< (ostream &out, Triple<A, B, C> t) { return out << "(" << t.st << ", " << t.nd << ", " << t.rd << ")"; }
template<class T> ostream& operator<<(ostream& out, vector<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class T> ostream& operator<<(ostream& out, set<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class L, class R> ostream& operator<<(ostream& out, map<L, R> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }

const int P = 1e9 + 7;
const int N = 1e7 + 7;
int spow(int a, int b) {
  int r = 1;
  while (b) {
    if (b % 2) {
      r = r * a % P;
    }
    a = a * a % P;
    b /= 2;
  }
  return r;
}
int fac[N];
int inv_fac[N];
int Newt(int a, int b) {
  return fac[a] * inv_fac[a - b] % P * inv_fac[b] % P;
}
int Prod(int a, int len) {
  return fac[a + len - 1] * inv_fac[a - 1] % P;
}
int32_t main() {

  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
  cin.tie(0);
  //double beg_clock = 1.0 * clock() / CLOCKS_PER_SEC;
  
  // policzmy takie permutacje ze wsrod pierwszych k nie ma petli i kazdy cykl zawiera cos z tych pierwszych k
  // zafiksujmy sobie zbior petelek przez incl-excl
  // k! * (k-petle)*(k+1)*...*(n-1)
  int n, a;
  cin>>n>>a;
  fac[0] = 1;
  RE (i, n) {
    fac[i] = i * fac[i - 1] % P;
  }
  inv_fac[n] = spow(fac[n], P - 2);
  FORD (i, n - 1, 0) {
    inv_fac[i] = inv_fac[i + 1] * (i + 1) % P;
  }
  // mamy k-petle dozwolonych
  // jak k<a to mamy jedno mniej
  // (k-petle)! * (k-petle)*(k-petle+1)*...*(n-petle-1)
  int res = 0;
  RE (k, a) {
    int outer = 0;
    FOR (petle, 0, k - 1) {
      int inner = Newt(k, petle);
      inner = inner * fac[k - petle] % P;
      if (k < a) {
        inner = inner * Prod(k - petle, n - a) % P;
        inner = inner * Prod(n - a + 1 + k - petle, a - k - 1) % P;
      } else {
        inner = inner * Prod(k - petle, n - a) % P;
      }
        //inner = inner * fac[n - (k < a) - petle - 1] % P;
//       if (k-petle-1 >= 0) {
//         inner = inner * inv_fac[k - 1 - petle] % P;
//       } else {
//         inner = 0;
      //}
      debug(k, petle, inner);
      if (petle % 2 == 0) {
        outer = (outer + inner) % P;
      } else {
        outer = (outer - inner + P) % P;
      }
    }
    debug(k, outer);
    res = (res + outer) % P;
  }
  cout<<res<<endl;
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return 0;
}


Measured memory_bytes: 159900