#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 5e3 + 10, mod = 998244353;
int n, k, a[N], p[N], f[N][N], s[N], fac[N];
map<int, int> id;
vector<int> t[N];
int idx, L[N], b[N], tot;
signed main() {
	ios::sync_with_stdio(0), cin.tie(0);
	cin >> n >> k, fac[0] = 1;
	for(int i = 1; i <= n; i ++) fac[i] = fac[i - 1] * i % mod;
	for(int i = 1; i <= n; i ++) {
		cin >> a[i];
		if(id[a[i] - k]) t[id[a[i] - k]].push_back(i), id[a[i]] = id[a[i] - k];
		else t[++ idx].push_back(i), id[a[i]] = idx;
	}
	for(int i = 1; i <= idx; i ++) {
		int ll = tot + 1;
		for(auto j : t[i]) L[++ tot] = ll;
	}
	f[0][0] = 1;
	for(int j = 1; j <= n; j ++) {
		s[0] = f[0][j - 1];
		for(int i = 1; i <= n; i ++)
			s[i] = (s[i - 1] + f[i][j - 1]) % mod;
		for(int i = 1; i <= n; i ++) {
			f[i][j] = f[i - 1][j - 1];
			if(i >= 2) f[i][j] += 2 * (s[i - 2] - (L[i] >= 2 ? s[L[i] - 2] : 0)) % mod;
			f[i][j] %= mod;
		}
	}
	int ans = 0;
	for(int i = 1; i <= n; i ++) {
		if(n - i & 1) ans = (ans - fac[i] * f[n][i]) % mod;
		else ans = (ans + fac[i] * f[n][i]) % mod;
	}
	cout << (ans + mod) % mod << '\n';
	
	return 0;
}