#include <bits/stdc++.h>
using namespace std;
#define fo(i,j,k) for(int i=(j),end_i=(k);i<=end_i;i++)
#define ff(i,j,k) for(int i=(j),end_i=(k);i< end_i;i++)
#define fd(i,j,k) for(int i=(j),end_i=(k);i>=end_i;i--)
#define all(x) (x).begin(),(x).end()
#define cle(x) memset(x,0,sizeof(x))
#define lowbit(x) ((x)&-(x))
#define VI vector<int>
#define ll long long
#define ull unsigned ll
#define lll __int128
#define db double
#define lb long db
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define endl "\n"
template<class T>inline void read(T &x) {
    x=0; char ch=getchar(); bool f=0;
    for(;ch<'0'||ch>'9';ch=getchar()) f|=(ch=='-');
    for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+(ch^48);
    if(f) x=-x;
}
template<class T, class... V>
inline void read(T &a, V&... b){read(a); read(b...);}
#ifndef ONLINE_JUDGE
#define debug(x) cerr<<#x<<"="<<x<<endl
#define debugv(x) cerr<<#x<<" : "; ff(i,0,(x).size()) cerr<<(x)[i]<<(i==(x).size()-1?'\n':' ')
#else
#define debug(x)
#define debugv(x)
#endif
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());

const ll mod = 998244353;
inline ll Pow(ll x,ll y) {
    ll ans = 1;
    for(; y; y >>= 1, x = x * x % mod)
        if(y & 1)
            ans = ans * x % mod;
    return ans;
}
inline ll Add(ll x,ll y) {
    x += y;
    return (x >= mod) ? x - mod : x;
}
inline ll Dec(ll x,ll y) {
    x -= y;
    return (x < 0) ? x + mod : x;
}
inline ll Mul(ll x,ll y) {
    return 1ll * x * y % mod;
}

const int N = 6e6 + 5;
const int S = 10;

namespace PAM {
	int n,s[N],num[N],p,las,nex[N][S],fail[N],len[N],sz[N];
	void init() {
		for(int i=0;i<=n;i++) s[i]=0;
		for(int i=1;i<=p;i++) len[i]=fail[i]=sz[i]=0,memset(nex[i],0,sizeof(nex[i]));
		s[n=0]=len[p=2]=-1;
		fail[las=1]=fail[2]=2;
	}
	int getfail(int x) {for(;s[n-1-len[x]]!=s[n];x=fail[x]); return x;}
	void add(int c, bool flag) {
		s[++n]=c;
		int cur=getfail(las);
		if(!nex[cur][c]) {
			len[++p]=len[cur]+2;
			fail[p]=nex[getfail(fail[cur])][c];
			if(!fail[p]) fail[p]=1;
			nex[cur][c]=p;
		}
		las=nex[cur][c];
		sz[las]++;
        if (flag) num[las] ++;
	}
    vector<int> adj[N];
    void dfs(int u) {
        for (auto v : adj[u]) {
            dfs(v);
            num[u] += num[v];
        }
    }
    ll work(int n) {
        fo(i,1,p) if (i != 2) adj[fail[i]].pb(i);
        dfs(2);
        ll ans = 0;
        fo(i,3,p)
            if (len[i] <=n)
                ans = Add(ans, Mul(len[i], Mul(num[i], num[i])));
        return ans;
    }
}
int n;
char s[N];
int main() {
    read(n);
    scanf("%s", s + 1);
    PAM::init();
    for (int i = 1; i <= n; i ++)
        PAM::add(s[i] - '0', 0);
    for (int i = 1; i <= n; i ++)
        PAM::add(s[i] - '0', 1);
    printf("%lld\n", PAM::work(n));
    return 0;
}