#include<bits/stdc++.h>
using namespace std;
#define MAXN 600005
#define ll long long
const ll mod = 998244353;

ll n, m;
char s[MAXN];
int kmp[MAXN];

struct SAM{
    int last = 1, tot = 1;
    int ch[MAXN<<1][26], len[MAXN<<1], f[MAXN<<1];
    void ins(char c) {
        c -= 'a';
        int p = last, cur = last = ++tot;
        len[cur] = len[p] + 1;
        for(;p && !ch[p][c]; p = f[p]) ch[p][c] = cur;
        if(!p) {f[cur] = 1; return;}
        int q = ch[p][c];
        if(len[q] == len[p] + 1) {f[cur] = q; return;}
        int clone = ++tot;
        for(int i=0;i<26;i++) ch[clone][i] = ch[q][i];
        f[clone] = f[q], len[clone] = len[p] + 1;
        f[q] = f[cur] = clone;
        for(;p && ch[p][c] == q; p = f[p]) ch[p][c] = clone;
    }
    ll calc() {
        ll ret = 0;
        for(int i=2;i<=tot;i++) ret += len[i] - len[f[i]];
        return ret % mod;
    }
} sam;

int main() {
    cin>>n>>m;
    scanf("%s", s+1);
    kmp[1] = 0;
    for(int i=2, j=0;i<=n;i++) {
        while(j && s[j+1] != s[i]) j = kmp[j];
        if(s[j+1] == s[i]) j++;
        kmp[i] = j;
    }
    int d = n;
    for(int x=kmp[n];x;x=kmp[x]) {
        if(n % (n - x) == 0) {d = n - x; break;}
    }
    m = m * (n / d);
    n = d;
    if(m == 1) {
        for(int i=1;i<=n;i++) sam.ins(s[i]);
        cout << sam.calc() << '\n';
    }else {
        for(int i=1;i<=n;i++) sam.ins(s[i]);
        for(int i=1;i<=n;i++) sam.ins(s[i]);
        ll ans = (sam.calc() + n * n % mod * ((m-2) % mod)) % mod;
        cout << ans << '\n';
    }
    return 0;
}