#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
using LL = long long;
const int maxn = 6e6 + 5;
struct Node{
    int fa, len, cnt;
    int ch[10];
}node[maxn];
char s[maxn];
int bk[maxn];
int tot = 1;

int get_fail(int x, int i){
    while(s[i - node[x].len - 1] != s[i]) x = node[x].fa;
    return x;
}

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);

    int n;
    cin >> n;
    for(int i = 1; i <= n; i++) 
        cin >> s[i], s[i + n] = s[i];
    node[0].fa = 1, node[1].len = -1;
    int last = 0;
    for(int i = 1; i <= n; i++){
        int c = s[i] - '0';
        int pos = get_fail(last, i);
        if (!node[pos].ch[c]){
            node[++tot].fa = node[get_fail(node[pos].fa, i)].ch[c];
            node[pos].ch[c] = tot;
            node[tot].len = node[pos].len + 2;
        }
        last = node[pos].ch[c];
        node[last].cnt++;
    }
    for(int i = tot; i; i--){
        node[node[i].fa].cnt += node[i].cnt;
    }
    for(int i = 0; i <= tot; i++){
        bk[i] = node[i].cnt;
        node[i].cnt = node[i].fa = node[i].len = 0;
        memset(node[i].ch, 0, sizeof node[i].ch);
    }
    node[0].fa = 1, node[1].len = -1;
    last = 0; tot = 1;
    for(int i = 1; i <= 2 * n; i++){
        int c = s[i] - '0';
        int pos = get_fail(last, i);
        if (!node[pos].ch[c]){
            node[++tot].fa = node[get_fail(node[pos].fa, i)].ch[c];
            node[pos].ch[c] = tot;
            node[tot].len = node[pos].len + 2;
        }
        last = node[pos].ch[c];
        node[last].cnt++;
    }
    for(int i = tot; i; i--){
        node[node[i].fa].cnt += node[i].cnt;
    }
    const int mod = 998244353;
    LL ans = 0;
    for(int i = 1; i <= tot; i++){
        if (node[i].len <= n){
            int cnt = node[i].cnt - bk[i];
            ans += 1LL * node[i].len * cnt % mod * cnt % mod;
            ans %= mod;
        }
    }
    cout << ans << '\n';

}