import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)


def comb(n, k):
    return fac[n] * pow(fac[k], mod - 2, mod) * pow(fac[n - k], mod - 2, mod)


n, m = map(int, readline().split())
mod = 10 ** 9 + 7
fac = [1] * (n + 1)
ans = 0
for i in range(2, n + 1):
    fac[i] = fac[i - 1] * i
    fac[i] %= mod
for i in range(m + 1):
    v = 1
    if i % 2 == 1:
        v = -1
    ans += v * comb(m, i) * pow(m - i, n, mod)
    ans %= mod
print(ans)