mod = 10 ** 9 + 7
def comb(n, r):
    if n < r:return 0
    if n < 0 or r < 0:return 0
    return fa[n] * fi[r] % mod * fi[n - r] % mod
n, m = map(int, input().split())
fa = [1] * (m + 1)
fi = [1] * (m + 1)
for i in range(1, m + 1):
    fa[i] = fa[i - 1] * i % mod
    fi[i] = pow(fa[i], mod - 2, mod)
ans = 0
for i in range(m + 1):
    cnt = comb(m, i) * pow(i, n, mod)
    if (m - i) & 1:
        ans -= cnt
    else:
        ans += cnt
print(ans % mod)