#yuki1035
mod=10**9+7
n,m=map(int,input().split())
res=0
c=1
for i in range(m+1):
 t=pow(i,n,mod)
 if (m+i)%2:
  t=mod-t
 res+=t*c
 c*=(m-i)*pow(i+1,mod-2,mod)
 c%=mod
print(res%mod)