MOD = 10**9+7
P,K = list(map(int,input().split()))

now = [1,0]
for _ in range(K):
    next = [0,0]
    next[0] += now[0] + now[0] * P + now[1] + now[1]
    next[0] %= MOD

    next[1] += now[0] * (P - 1) + now[1] * (P - 1) + now[1] * (P - 1)
    next[1] %= MOD

    now,next = next,now
print(now[0])