#include<bits/stdc++.h>
using namespace std;
const int mo = 998244353;
struct PAM {
    static constexpr int ALPHABET_SIZE = 28;
    struct Node {
        int len; // 当前节点最长回文长度
        int fail;// 回文树边
        int scnt; // 当前节点表示的回文后缀的本质不同回文串个数
        int pcnt; // 当前节点回文串在字符串中出现次数，每个点代表一个不同的回文串
        std::array<int, ALPHABET_SIZE> next;
        Node() : len{}, fail{}, scnt{}, next{}, pcnt{} {}
    };
    std::vector<Node> t;
    int last;
    std::string s;
    PAM() {
        init();
    }
    void init() {
        t.assign(2, Node());
        t[1].len = -1;
        last = 0;
        t[0].fail = 1;
        s = "$";
    }
    int newNode() {
        t.emplace_back();
        return t.size() - 1;
    }
    int get_fail(int x) {
        int pos = s.size() - 1;
        while(s[pos - t[x].len - 1] != s[pos]) x = t[x].fail;     
        return x;
    }
    void add(char c, int w, char offset = 'a') {
        s += c;
        int let = c - offset;
        int x = get_fail(last);
        if (!t[x].next[let]) {  
            int now = newNode();
            t[now].len = t[x].len + 2;
            t[now].fail = t[get_fail(t[x].fail)].next[let];
            t[x].next[let] = now;
            t[now].scnt = t[t[now].fail].scnt + 1;
        }
        last = t[x].next[let];
        t[last].pcnt += w;
    }
    int calc() {
        int ans = 0;int n = int(s.size()) / 2;
        for(int i = t.size() - 1;i >= 2;i --) {
            t[t[i].fail].pcnt += t[i].pcnt;
            if(t[i].len <= n)ans = (ans + 1ll * t[i].pcnt * t[i].pcnt % mo * t[i].len % mo) % mo;
        }
        return ans;
    }
};
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    string s;
    cin >> s;
    PAM pam;
    for(int i = 0;i < n;i ++) {
        pam.add(s[i],0,'0');
    }
    for(int i = 0;i < n;i ++) {
        pam.add(s[i],1,'0');
    }
    int ans = pam.calc();
    cout << ans << endl;
}