#include <bits/stdc++.h>

const int N = 3001000;
const int mod = 998244353;

int n;
char str[N];

namespace PAM {
    int cur_len, str[N * 2];

    int nClock, Last;
    struct node {
        int trans[26];
        int link, len;
    } t[N * 2];

    int cnt[N * 2];
    std::vector<int> son[N * 2];

    void init() {
        t[0].len = 0, t[0].link = 1;
        t[1].len = -1;

        str[cur_len = 0] = -1;
        nClock = 1, Last = 1;
    }

    int find(int p) {
        while (str[cur_len - t[p].len - 1] != str[cur_len]) p = t[p].link;
        return p;
    }

    void extend(int c, int type) {
        str[++ cur_len] = c;

        int p = find(Last);
        if (!t[p].trans[c]) {
            int np = ++ nClock;

            t[np].len = t[p].len + 2;
            t[np].link = t[find(t[p].link)].trans[c];

            t[p].trans[c] = np;
        }

        Last = t[p].trans[c];

        if (type) cnt[Last] ++;
    }

    void build_tree() {
        son[1].push_back(0);
        for (int i = 2; i <= nClock; i ++) son[t[i].link].push_back(i);
    }

    void dfs(int u) {
        for (int v : son[u]) {
            dfs(v);
            cnt[u] += cnt[v];
        }
    }

    int calc() {
        int ans = 0;
        for (int i = 2; i <= nClock; i ++)
            if (t[i].len <= n)
                ans = (ans + 1ll * cnt[i] * cnt[i] % mod * t[i].len) % mod;
        return ans;
    }
}

int main() {
    scanf("%d", &n);
    scanf("%s", str + 1);

    PAM::init();

    for (int i = 1; i <= n; i ++) PAM::extend(str[i] - '0', 0);
    for (int i = 1; i <= n; i ++) PAM::extend(str[i] - '0', 1);

    PAM::build_tree();
    PAM::dfs(1);

    printf("%d\n", PAM::calc());

    return 0;
}