import sys
n,m=map(int,sys.stdin.readline().split())
M=10**9+7
I=[1]*(m+1);F=[1]*(m+1);R=[1]*(m+1)
for i in range(2,m+1):
	I[i]=(M-M//i)*I[M%i]%M
	F[i]=i*F[i-1]%M
	R[i]=I[i]*R[i-1]%M
r=0
for k in range(m):
	r=(r+(-1)**k*F[m]*R[k]*R[m-k]*pow(m-k,n,M))%M
print(r)