#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <utility>
#include <cmath>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <numeric>
#include <functional>
#include <atcoder/convolution>
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define exrep(i, a, b) for(ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll mod = 998244353;
const ll INF = 1e16;

const ll MAX = 500010;

ll fact[MAX];  // fact[i] : iの階乗のmod
ll inv[MAX];  // inv[i] : iの逆数のmod
ll invfact[MAX];  // invfact[i] : iの階乗の逆数のmod

void init() {
    fact[0] = 1;
    inv[0] = inv[1] = 1;
    invfact[0] = 1;
    for(ll i = 1; i < MAX; i++) {
        fact[i] = i * fact[i-1] % mod;
        if(i >= 2) {
            inv[i] = mod - inv[mod % i] * (mod / i) % mod;
        }
        invfact[i] = invfact[i-1] * inv[i] % mod;
    }
}

int main() {
    ll n, k;
    cin >> n >> k;

    init();

    vl b(n+1);    
    rep(i, n) {
        b[i+1] = (b[i] + invfact[i]) % mod;
    }

    vl d(n+1);
    ll z = 1;
    exrep(i, 1, n) {
        ll m;
        cin >> m;
        d[i] = (m + 1) % mod;
        z = z * m % mod;
    }
    vl e(n+1);
    exrep(i, 1, n) {
        e[i] = d[n - i];
    }

    vl v = convolution<mod>(d, e);

    ll x = fact[n-1] * (b[n-1] + mod - b[n - k - 1]) % mod;

    ll ans = 0;
    exrep(l, 1, n-1) {
        ll y = b[n - l - 1];
        if(0 <= n - l - k - 1) {
            y += mod - b[n - l - k - 1];
            y %= mod;
        }
        y = y * fact[n - l - 1] % mod;
        ans += v[n + l] * (x + mod - y);
        ans %= mod;
    }

    ans = ans * z % mod * inv[4] % mod;

    out(ans);
    re0;
}