#include<bits/stdc++.h>
#define deg(a) cout << #a << '=' << a << "\n"
#define all(a) a.begin(),a.end()
#define lowbit(x)  ((x)&(-x))
#define find1(x)  (__builtin_popcount(x))
#define pll pair<int,int>
// #define int long long
#define endl '\n'
#define ff first
#define ss second
#define ULL unsigned long long 
#define lc p << 1
#define rc p << 1|1
using namespace std;
using i64 = long long;
const int N = 2e5+10;
const int M = 3e6+10;
const int mod2 = 998244353;
const int mod1 = 1e9+7;
const int maxn = 6e6 + 10;
namespace pam {
int sz, tot, last;
int cnt[maxn], ch[maxn][26], len[maxn], fail[maxn];
char s[maxn];
int node(int l) {  // 建立一个新节点，长度为 l
  sz++;
  memset(ch[sz], 0, sizeof(ch[sz]));
  len[sz] = l;
  fail[sz] = cnt[sz] = 0;
  return sz;
}

void clear() {  // 初始化
  sz = -1;
  last = 0;
  s[tot = 0] = '$';
  node(0);
  node(-1);
  fail[0] = 1;
}

int getfail(int x) {  // 找后缀回文
  while (s[tot - len[x] - 1] != s[tot]) x = fail[x];
  return x;
}

void insert(char c,int w) {  // 建树
  s[++tot] = c;
  int now = getfail(last);
  if (!ch[now][c - 'a']) {
    int x = node(len[now] + 2);
    fail[x] = ch[getfail(fail[now])][c - 'a'];
    ch[now][c - 'a'] = x;
  }
  last = ch[now][c - 'a'];
  cnt[last] += w;
  // return len[last];
}
}  // namespace pam

signed main() {
  pam::clear();
  int n;
  cin >> n;
  string s;
  cin >> s;
  // string s1 = s;
  // reverse(s1.begin(),s1.end());
  for (int i = 0; i < s.size(); i++) {
        pam::insert(s[i],0);
  }
  for (int i = 0; i < s.size(); i++) {
        pam::insert(s[i],1);
  }
  for(int i = pam::sz; i >= 2 ; i--) {
        pam::cnt[pam::fail[i]] += pam::cnt[i];
  }
  long long  ans = 0;
  for (int i = 0; i <= pam::sz; i++) {  // 更新答案
    if(pam::len[i] > n) continue;
    ans = (ans + 1ll * ((long long)pam::len[i] * ((long long)pam::cnt[i] * (long long)pam::cnt[i]) % mod2) % mod2) % mod2;
  }
  cout << ans << endl;
}