mod=10**9+7
n,m=map(int,input().split())
fact=[1]
for i in range(1,n+1):
    fact.append((fact[-1]*i)%mod)
revfact=[1]
for i in range(1,n+1):
    revfact.append(pow(fact[i],mod-2,mod))
ans=0
for i in range(0,m+1):
    ans+=pow(-1,i)*(fact[m]*revfact[i]*revfact[m-i])*pow(m-i,n,mod)
    ans%=mod
print(ans)