mod = 998244353

max_kai = 10**6+10
kai = [1] * max_kai
for i in range(1, max_kai):
    kai[i] = kai[i-1] * i % mod
kkai = [0] * max_kai
kkai[-1] = pow(kai[-1], mod - 2, mod)
for i in reversed(range(1, max_kai)):
    kkai[i - 1] = kkai[i] * i % mod

kkai_sum = [0]*(max_kai+1)
for i in range(max_kai):
    kkai_sum[i+1] = (kkai_sum[i] + kkai[i]) % mod


def cutsum(a, b):
    return kkai_sum[a] - kkai_sum[max(0, b)]


def fft_inplace(a, w):
    n = len(a)
    m = n
    t = 1
    while m >= 2:
        mh = m >> 1
        for i in range(0, n, m):
            for s in range(mh):
                j, k = i+s, i+mh+s
                a[j], a[k] = (a[j]+a[k]) % mod, (a[j]-a[k])*w[s*t] % mod
        m = mh
        t *= 2


def ifft_inplace(a, w):
    n = len(a)
    m = 2
    t = -(n >> 1)
    while m <= n:
        mh = m >> 1
        for i in range(0, n, m):
            for s in range(mh):
                j, k = i+s, i+mh+s
                a[k] *= w[s*t]
                a[j], a[k] = (a[j]+a[k]) % mod, (a[j]-a[k]) % mod
        m <<= 1
        t //= 2
    n_inv = pow(n, mod-2, mod)
    for i in range(n):
        a[i] = a[i] * n_inv % mod


def convolution(a, b):
    n2 = max(len(a) + len(b), 1)
    n = 1 << (n2-1).bit_length()
    a = a + [0] * (n-len(a))
    b = b + [0] * (n-len(b))

    w_root = pow(3, (mod-1)//n, mod)
    w = [1] * n
    for i in range(1, n):
        w[i] = w[i-1] * w_root % mod

    fft_inplace(a, w)
    fft_inplace(b, w)
    for i, j in enumerate(b):
        a[i] = a[i] * j % mod
    ifft_inplace(a, w)
    return a[:n2]


n, k = map(int, input().split())
m = [int(i)+1 for i in input().split()]
b = convolution(m, m[::-1])
ans = 0

for i in range(n):
    ans += (kai[n-1] * cutsum(n-1, n-k-1) - kai[i]*cutsum(i, i-k)) % mod * b[i]
    ans %= mod
for i in m:
    ans *= i-1
    ans %= mod
ans *= pow(4, mod-2, mod)
ans %= mod
print(ans)