#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
using LL = long long;

const int maxn = 1.2e6 + 5;
struct SuffixAutomaton{
    struct Node{
        int len, fa;
        int ch[26];
    }node[maxn];
    int tot = 1, last = 1;
    // int f[maxn], c[maxn], id[maxn];

    SuffixAutomaton(){
        clear();
    }

    int new_node(){
        ++tot;
        node[tot].len = node[tot].fa = 0;
        memset(node[tot].ch, 0, sizeof node[tot].ch);
        // f[tot] = 0; 
        return tot;
    }

    void clear(){
        tot = 0;
        last = new_node();
    }

    void extend(int c){
        int p = last, np = last = new_node();
        node[np].len = node[p].len + 1;
        for(; p && !node[p].ch[c]; p = node[p].fa) node[p].ch[c] = np;
        if (!p) node[np].fa = 1;
        else{
            int q = node[p].ch[c];
            if (node[q].len == node[p].len + 1) node[np].fa = q;
            else{
                int nq = new_node();
                node[nq] = node[q], node[nq].len = node[p].len + 1;
                node[q].fa = node[np].fa = nq;
                for(; p && node[p].ch[c] == q; p = node[p].fa) node[p].ch[c] = nq;
            }
        }
        // f[last] += 1;
    }   

    void build(const string &s){
        clear();
        for(auto c : s) extend(c - 'a');
    }

    LL get(int n){
        LL ans = 0;
        for(int i = 2; i <= tot; i++){
            int l = node[node[i].fa].len + 1;
            int r = min(n, node[i].len);
            if (l <= r) ans += r - l + 1; 
        }
        return ans;
    }

}sam;

vector<int> KMP(string s){
    const int n = (int)s.size();
    s = " " + s;
    vector<int> fail(n + 1);
    for(int i = 2, j = 0; i <= n; i++){
        while(j && s[j + 1] != s[i]) j = fail[j];
        if (s[j + 1] == s[i]) j++;
        fail[i] = j;
    }
    return fail;
}

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    
    const int mod = 998244353;
    int n, m;
    cin >> n >> m;
    string s;
    cin >> s;

    if (m == 1){
        sam.build(s);
        cout << sam.get(n) % mod << '\n';
        return 0;
    }

    auto fail = KMP(s);
    int period = n;
    {
        int t = n;
        while(n % (n - fail[t]) != 0){
            t = fail[t];
        }
        period = n - fail[t];
    }

    s += s;
    sam.build(s);
    LL sum = sam.get(n) % mod;
    // [n + 1, n * m - period]
    sum += period * (1LL * n * m % mod - period - n);
    sum += 1LL * period * (period + 1) / 2;
    cout << (sum % mod + mod) % mod << '\n';

}