import sys

input = sys.stdin.buffer.readline
MOD = 998244353


def prec_fact(n):
    fact = [1] * (n + 1)
    inv_fact = [1] * (n + 1)
    for i in range(2, n + 1):
        fact[i] = fact[i - 1] * i % MOD
    inv_fact[n] = pow(fact[n], MOD - 2, MOD)
    for i in range(n, 2, -1):
        inv_fact[i - 1] = inv_fact[i] * i % MOD
    return fact, inv_fact


def main():
    N, M = map(int, input().split())
    K = list(map(int, input().split()))
    K_max = max(K)
    fact, inv_fact = prec_fact(N + K_max)
    acc = 1
    for i in range(N - 1):
        acc = acc * (N + M - i) % MOD
    A = [0] * (K_max + 2)
    for j in range(K_max + 1):
        acc = acc * (M - j + 1) % MOD
        x = fact[N + j - 1] * inv_fact[N - 1] % MOD
        x = x * acc % MOD
        A[j] = x * inv_fact[N + j] % MOD
    M_inv = pow(M, MOD - 2, MOD)
    s2 = [0]
    B = [0] * (K_max + 1)
    for i in range(K_max + 1):
        nxs2 = [0] * (i + 2)
        nxs2[i] = 1
        for k in range(1, i + 1):
            nxs2[k] = (s2[k - 1] + s2[k] * k) % MOD
        s2 = nxs2
        acc = 0
        x = sum(s2j * A[j] for j, s2j in enumerate(s2)) % MOD
        B[i] = x * pow(-M_inv, i, MOD) % MOD
    K_freq = [0] * (K_max + 1)
    for k in K:
        K_freq[k] += 1
    ans = 0
    acc = 1
    for k, freq in enumerate(K_freq):
        if freq:
            for i in range(k + 1):
                x = freq * B[i] % MOD
                x = x * fact[k] % MOD
                x = x * inv_fact[k - i] % MOD
                x = x * inv_fact[i] % MOD
                x = x * acc % MOD
                ans += x
        acc = acc * M % MOD
    print(ans % MOD)


if __name__ == "__main__":
    main()