P = 10**9+7
def pow(b,e)
	ret = 1
	while e > 0
		if (e&1) == 1 then
			ret = ret * b % P
		end
		b = b * b % P
		e>>=1
	end
	return ret
end
N,M = gets.split().map{|s| s.to_i}
f = [0]*(M+1)
fi = [0]*(M+1)
f[0] = 1
(1..M).each{|i| f[i] = i*f[i-1]%P}
fi[M] = pow(f[M],P-2)
(1..M).reverse_each{|i| fi[i-1] = i*fi[i]%P}
p (0..M-1).map{|k| f[M]*fi[k]*fi[M-k]*pow(M-k,N)*((-1)**(k%2)) % P}.inject(:+) % P