mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    P, K = map(int, input().split())

    dp_0 = [0] * (K+1)
    dp_1 = [0] * (K+1)
    dp_0[0] = 1
    for i in range(K):
        # add
        dp_0[i+1] = (dp_0[i] + dp_1[i])%mod
        dp_1[i+1] = ((dp_0[i] + dp_1[i]) * (P-1))%mod
        # mult
        dp_0[i+1] = (dp_0[i+1] + (dp_0[i] * P)%mod + dp_1[i])%mod
        dp_1[i+1] = (dp_1[i+1] + dp_1[i] * (P-1))%mod
    print(dp_0[-1])


if __name__ == '__main__':
    main()