/* Problem URL: https://codeforces.com/gym/106054/problem/B */

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;

#define V vector

#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)

#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)

#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()

using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;

using ll = long long;

using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;

template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
    os << vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        os << ' ' << vec[i];
    }
    os << '\n';
    return os;
}

template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
    for (auto &i : vec) {
        is >> i;
    }
    return is;
}

template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
    for (auto &i : vec) {
        os << i[0];
        for (size_t j = 1; j < i.size(); j++) {
            os << ' ' << i[j];
        }
        os << '\n';
    }
    return os;
}

template<class v>
auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
    for (auto &i : vec) {
        for (auto &j : i) {
            is >> j;
        }
    }
    return is;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, k;
    cin >> n >> k;

    const ll mod = 998244353;

    auto fpow = [&](ll a, ll p) {
        ll ans = 1;

        rep(i, 31) {
            if ((p >> i) & 1) {
                ans *= a;
                ans %= mod;
            }
            
            a *= a;
            a %= mod;
        }

        return ans;
    };

    auto comb = [&](ll n, ll k) {
        ll ans = 1;
        ll div = 1;

        rep(i, k) {
            ans *= (n - i);
            ans %= mod;

            div *= (i + 1);
            div %= mod;
        }

        return (ans * fpow(div, mod - 2)) % mod;
    };

    vl b(n - k + 1);
    cin >> b;

    ll ans = b[0];
    
    rep(i, k) {
        ll m = 0;
        ll tmp = 0;
        for (int j = i; j + 1 < b.size(); j += k) {
            m += b[j] - b[j + 1];
            rmax(tmp, m);
        }

        ans -= tmp;
    }

    if (ans < 0) {
        cout << "0\n";
        return 0;
    }

    cout << comb(ans + k - 1, k - 1) << '\n';
}