MOD = 10**9+7
N,M = map(int,input().split())
A = list(range(M+1))
A[0]=A[1]=1
for i in range(2,M+1):
    A[i]=(i*A[i-1])%MOD
B = [0]*(M+1)
B[0]=B[1]=1
B[M] = pow(A[M],MOD-2,MOD)
for i in range(M-1,1,-1):
    B[i] = (B[i+1]*(i+1))%MOD
def comb(n,k):
    if k>n or k<0:return 0
    if k==0 or k==n:return 1
    return (A[n]*B[k]*B[n-k])%MOD
ans = 0
for k in range(M):
    ans = (ans+(-1)**(k%2)*comb(M,k)*pow(M-k,N,MOD))%MOD
print(ans)