n,m = map(int,input().split())
mod = 10**9+7

N = m+5
fact = [1]*N
finv = [1]*N
 
for i in range(2,N):
    fact[i] = (fact[i-1]*i)%mod
finv[-1] = pow(fact[-1],mod-2,mod)
for i in range(1,N)[::-1]:
    finv[i-1] = (finv[i]*i)%mod

def nCr(n,r):
    if r > n:
        return 0
    else: 
        return fact[n]*finv[r]%mod*finv[n-r]%mod



ans = 0
for i in range(1,m+1):

    calc = nCr(m,i)*pow(i,n,mod)
    if (m-i)%2:
        calc = -calc
    ans += calc
    ans %= mod
print(ans)