N, M = map(int, input().split())
if N < M:
    print(0)
    exit(0)
r, c = 0, 1
for i in range(M):
    r += (-1) ** i * c * pow(M - i, N, (10 ** 9 + 7))
    r %= (10 ** 9 + 7)
    c *= M -  i
    c %= (10 ** 9 + 7)
    c *= pow(i + 1, (10 ** 9 + 7) - 2, (10 ** 9 + 7))
    c % (10 ** 9 + 7)
print(r)