class Twelvefold(): #n <= 1000程度
    def __init__(self, n, mod, build=True):
        self.mod = mod
        self.fct = [0 for _ in range(n + 1)]
        self.inv = [0 for _ in range(n + 1)]
        self.fct[0] = 1
        self.inv[0] = 1
        for i in range(n):
            self.fct[i + 1] = self.fct[i] * (i + 1) % mod
        self.inv[n] = pow(self.fct[n], mod - 2, mod)
        for i in range(n)[::-1]:
            self.inv[i] = self.inv[i + 1] * (i + 1) % mod
        if build: self.build()

    def build(self):
        self.stl = [[0 for j in range(n + 1)] for i in range(n + 1)]
        self.bel = [[0 for j in range(n + 1)] for i in range(n + 1)]
        self.prt = [[0 for j in range(n + 1)] for i in range(n + 1)]
        self.stl[0][0] = 1
        self.bel[0][0] = 1
        for i in range(n):
            for j in range(n):
                self.stl[i + 1][j + 1] = self.stl[i][j] + (j + 1) * self.stl[i][j + 1]
                self.stl[i + 1][j + 1] %= self.mod
        for i in range(n):
            for j in range(n):
                self.bel[i + 1][j + 1] = self.bel[i + 1][j] + self.stl[i + 1][j + 1] % mod
                self.bel[i + 1][j + 1] %= self.mod
        for j in range(n):
            self.prt[0][j] = 1
        for i in range(n):
            for j in range(n):
                if i - j >= 0:
                    self.prt[i + 1][j + 1] = self.prt[i + 1][j] + self.prt[i - j][j + 1]
                else:
                    self.prt[i + 1][j + 1] = self.prt[i + 1][j]
                self.prt[i + 1][j + 1] %= self.mod

    def solve(self, element, subset, equate_element=False, equate_subset=False, less_than_1=False, more_than_1=False):
        assert not less_than_1 or not more_than_1
        n = element
        k = subset
        a = equate_element
        b = equate_subset
        c = less_than_1
        d = more_than_1
        id = a * 3 + b * 6 + c + d * 2
        tw = [self.tw1, self.tw2, self.tw3, self.tw4, self.tw5, self.tw6, self.tw7, self.tw8, self.tw9, self.tw10, self.tw11, self.tw12]
        return tw[id](n, k)

    def tw1(self, n, k):
        return pow(k, n, self.mod)

    def tw2(self, n, k):
        if k - n < 0: return 0
        return self.fct[k] * self.inv[k - n] % self.mod

    def tw3(self, n, k):
        return self.stl[n][k] * self.fct[k] % self.mod

    def tw4(self, n, k):
        if k == 0: return 0
        return self.fct[n + k - 1] * self.inv[n] * self.inv[k - 1] % self.mod

    def tw5(self, n, k):
        if k - n < 0: return 0
        return self.fct[k] * self.inv[n] * self.inv[k - n] % self.mod

    def tw6(self, n, k):
        if n - k < 0 or k == 0: return 0
        return self.fct[n - 1] * self.inv[k - 1] * self.inv[n - k]

    def tw7(self, n, k):
        return self.bel[n][k]

    def tw8(self, n, k):
        if k - n < 0: return 0
        return 1

    def tw9(self, n, k):
        return self.stl[n][k]

    def tw10(self, n, k):
        return self.prt[n][k]

    def tw11(self, n, k):
        if k - n < 0: return 0
        return 1

    def tw12(self, n, k):
        if n - k < 0: return 0
        return self.prt[n - k][k]

n, k = map(int, input().split())
t = Twelvefold(1000, 10**9 + 7, 0)
print(t.solve(n, k, 1, 0, 1, 0))


Measured memory_bytes: 5752