f=[1]*10**6;g=[1]*len(f);mod=10**9+7
for i in range(1,len(f)):
    f[i]=f[i-1]*i%mod
g[-1]=pow(f[-1],mod-2,mod)
for i in range(len(f)-1,0,-1):
    g[i-1]=g[i]*i%mod
ans=0
n,m=map(int,input().split());d=1
for i in range(m,0,-1):
    ans+=pow(i,n,mod)*f[m]%mod*g[i]%mod*g[m-i]%mod*d
    ans%=mod;d*=-1
print(ans)