n,m=map(int,input().split())
if n<m:
  print(0)
  exit()
M=10**9+7
fa=[1,1]
fb=[1,1]
for i in range(2,m+1):
  fa+=[fa[-1]*i%M]
  fb+=[fb[-1]*(M//i)*fb[M%i]*fa[M%i-1]*(-1)%M]
c=lambda n,k:fa[n]*fb[k]*fb[n-k]%M if n>=k else 0
print(sum(((-1)**(i%2))*c(m,i)*pow(m-i,n,M) for i in range(m+1))%M)