mod=1000000007
maxM=100010
fact=[0]*maxM
fact[0]=1
for i in range(1,maxM):
    fact[i]=fact[i-1]*i%mod
ifact=[0]*maxM
for i in range(maxM):
    ifact[i]=pow(fact[i],mod-2,mod)
def comb(n,k):
    if k<0 or k>n:
        return 0
    return fact[n]*ifact[k]*ifact[n-k]%mod
N,M=map(int,input().split())
ans=0
for i in range(M):
    if i%2==0:
        ans=(ans+comb(M,i)*pow(M-i,N,mod))%mod
    else :
        ans=(ans-comb(M,i)*pow(M-i,N,mod))%mod
        ans=(ans+mod)%mod
print(ans)