def prepare(n, MOD):
 
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
     
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
     
    return fn, invs

def cmb(n,r,fn,invs,mod):
    return fn*invs[r]*invs[n-r]%mod

n,m=map(int,input().split())
mod=10**9+7
fn,invs=prepare(m,mod)
a=[0]*(m+1)
for i in range(1,m+1):
    a[i]=(cmb(m,i,fn,invs,mod)*pow(i,n,mod)-a[i-1])%mod
print(a[m])