#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	if ((n < m) || (0 == m) || (0 == n)) {
		cout << 0 << endl;
		return 0;
	}
	vector<vector<long long>>v(n);
	v[0] = { 0,1 };
	rep(i, n - 1) {
		// *(x-(i+1))
		v[i + 1].resize(i + 3);
		rep(j, v[i].size()) {
			v[i + 1][j] -= v[i][j] * (i + 1);
			v[i + 1][j + 1] += v[i][j];
		}
	}
	vector<long long>ans(n);
	vector<long long>dp(n + 1);
	dp[n] = 1;
	rrep(i, n) {
		long long x = dp[i + 1];
		rep(j, v[i].size()) {
			dp[j] -= x * v[i][j];
		}
		ans[i] = x;
	}
	long long val = ans[m - 1];
	rep2(i, 1, m + 1) {
		val *= i;
	}
	cout << val << endl;
	return 0;
}