#include<bits/stdc++.h>
#define ll long long
#define re register
#define il inline
#define N 6000006
#define mod 998244353
using namespace std;
char s[N];
int las,ch[N][26],len[N],fail[N],ct,n;
ll cnt[N],tmp[N];
void init() {
	ct=1;las=0;
	s[0]='*';
	len[0]=0;fail[0]=1;
	len[1]=-1;fail[1]=1;
}

int getfail(int pos,int x) { while(s[pos-len[x]-1]!=s[pos]) x=fail[x];return x;}

void insert(int pos,char c) {
	int nw=getfail(pos,las);
	if(!ch[nw][c-'a']) {
		len[++ct]=len[nw]+2;
		fail[ct]=ch[getfail(pos,fail[nw])][c-'a'];
		ch[nw][c-'a']=ct;
	}
	++cnt[las=ch[nw][c-'a']];
}

ll solve() {
	ll ans=0;
	for(int i=ct;i>=0;--i) cnt[fail[i]]=(cnt[fail[i]]+cnt[i])%mod;
	for(int i=ct;i>=0;--i) tmp[fail[i]]=(tmp[fail[i]]+tmp[i])%mod;
	for(int i=2;i<=ct;++i) cnt[i]=(cnt[i]-tmp[i]+mod)%mod;
	for(int i=2;i<=ct;++i) if(len[i]<=n) ans=(cnt[i]*len[i]%mod*cnt[i]%mod+ans)%mod;
	return ans;
}

int main()
{
	cin>>n>>(s+1);
	init();
	for(int i=1;i<=n;++i) s[n+i]=s[i]; 
	for(int i=1;i<=n;++i) insert(i,s[i]);
	for(int i=0;i<=ct;++i) tmp[i]=cnt[i];
	for(int i=n+1;i<=2*n;++i) insert(i,s[i]);
	cout<<solve();
	return 0;
}