MOD = 10**9+7
n, m = map(int, raw_input().split())
if n<m:
    print 0
    exit(0)
ans = 0
fact = [1]*(m+1)
for i in xrange(1, m+1):
    fact[i] = (fact[i-1]*i) % MOD
ans = pow(m, n, MOD)
for i in xrange(1, m):
    res = pow(m-i, n, MOD)*fact[m]*pow(fact[i], MOD-2, MOD)*pow(fact[m-i], MOD-2, MOD)
    ans = (ans + res) % MOD if i%2==0 else (ans - res + MOD) % MOD
print ans