#include <bits/stdc++.h>
#include<vector>
#define ll long long
#define pii pair <int, int>
#define fi first
#define se second
#define pb push_back
#define ull unsigned long long

using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 2e5+5, M = 2e7+5, mod = 998244353; 
int n, k, id[M], f[M], cnt[N]; 
ll lv[45]; 
struct node {
	int sz, len, fa, ch[6]; 
}v[M];
vector <int> pr; 
int las, tot, o[45]; 
inline int tr (int p, int k) { return k > v[p].sz ? 0 : k; }
void upd (int k) {
//	cout << "INS:" << k << endl; 
	int p = las, cur = ++tot; 
	v[cur].sz = v[p].sz+(tr(p, k) == 0); v[cur].len = v[p].len+1;
//	cout << "NEW:" << cur << " " << v[cur].sz << " " << "CHECK_FA:" << las << " " << v[las].fa << endl; 
//	cout << "CHECK:" << v[2].sz << endl ;
	las = cur;  
	while (p && !v[p].ch[tr(p, k)]) {
//		cout << p << " " << v[p].sz << " " << v[cur].sz << endl; 
		if (v[p].sz+(tr(p, k) == 0) < v[cur].sz) {
			int nc = ++tot; 
			v[nc].sz = v[p].sz+(tr(p, k) == 0); v[nc].len = v[p].len+1; 
			v[cur].fa = nc; cur = nc; 
		} 
		v[p].ch[tr(p, k)] = cur; 
		p = v[p].fa; 
	}
	if (!p) return v[cur].fa = 1, void(); 
	int q = v[p].ch[tr(p, k)];
	if (v[q].len == v[p].len+1) return v[cur].fa = q, void(); 
	int cl = ++tot; v[cl] = v[q]; v[cl].sz = v[p].sz+(tr(p, k) == 0); v[cl].len = v[p].len+1; v[q].fa = v[cur].fa = cl; 
	while (p && v[p].ch[tr(p, k)] == q) v[p].ch[tr(p, k)] = cl, p = v[p].fa; 
}

string str; 
void solve () {
	cin >> n >> k; 
	lv[0] = 1; for (int i = 1;i < k;i++) lv[i] = lv[i-1]*(k-i)%mod; 
	ll s = k, ans = 0; 
	for (int i = 1;i <= n;i++) {
		while (tot) {
			memset(v[tot].ch, 0, sizeof v[tot].ch); 
			v[tot].sz = v[tot].len = v[tot].fa = 0; 
			tot--; 
		}
		las = tot = 1; 
		pr.clear(); memset(o, 0, sizeof o); 
		cin >> str;
		for (char j : str) {
			int x = j-'a'; 
			if (o[x]) {
				int id = 0; 
				for (int p = pr.size()-1;~p;p--) if (pr[p] == x) {
					id = p; break; 
				}
				upd(pr.size()-id); 
				pr.erase(pr.begin()+id); pr.push_back(x); 
			}
			else {
				upd(0); pr.push_back(x); o[x] = 1; 
			}
		}
		memset(f, 0, tot+1<<3); 
		for (int j = 0;j <= k;j++) if (v[1].ch[j]) f[v[1].ch[j]] = s; s = 0; 
		memset(cnt, 0, str.size()+1<<2); 
		for (int j = 2;j <= tot;j++) ++cnt[v[j].len]; 
		for (int j = 1;j <= str.size();j++) cnt[j] += cnt[j-1]; 
		for (int j = 2;j <= tot;j++) id[cnt[v[j].len]--] = j; 
		for (int J = 1;J < tot;J++) {
			int j = id[J]; (ans += lv[v[j].sz-1]*f[j]) %= mod; 
			int ss = 0; 
			for (int p = 0;p <= k;p++) if (v[j].ch[p]) (f[v[j].ch[p]] += f[j]) %= mod, ++ss; 
			if (v[j].ch[0]) (s += f[j]*lv[v[j].sz-1]%mod*(v[j].sz+1-ss)) %= mod; 
			else (s += f[j]*lv[v[j].sz-1]%mod*(k-ss)) %= mod;  
		}
	}
	cout << (ans+mod+1)%mod; 
}

signed main () {
	int T = 1;
	while (T--) solve();
	return 0;
}