/*
ID: LinKArftc
PROG: 3664.cpp
LANG: C++
*/

#include <map>
#include <set>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <cstdio>
#include <string>
#include <utility>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define eps 1e-8
#define randin srand((unsigned int)time(NULL))
#define input freopen("input.txt","r",stdin)
#define debug(s) cout << "s = " << s << endl;
#define outstars cout << "*************" << endl;
const double PI = acos(-1.0);
const double e = exp(1.0);
const int inf = 0x3f3f3f3f;
const int INF = 0x7fffffff;
typedef long long ll;

const int maxn = 1010;
const int MOD = 1000000007;

ll dp[maxn][maxn];
int n, k;

void init() {
    dp[1][0] = 1;
    dp[1][1] = 0;
    for (int i = 1; i <= 1000; i ++) {
        for (int j = 0; j <= 1000; j ++) {
            dp[i+1][j] = (dp[i+1][j] % MOD + (j + 1) * dp[i][j] % MOD) % MOD;
            dp[i+1][j+1] = (dp[i+1][j+1] % MOD + (i - j) * dp[i][j] % MOD) % MOD;
        }
    }
}

int main() {

    init();
    while (~scanf("%d %d", &n, &k)) {
        printf("%d\n", dp[n][k]);
    }

    return 0;
}