#include<iostream>
#include<algorithm>
#include<string>
#include<cstring>
#include<cstdio>
using namespace std;
const int N=3e6+10;
const int mod=998244353;
int i,j,n,m,k,l,a[N*4],tree[N*4][11],root,num,r,d[N*4],wz,f[N*4][24],pos[N*4],g[N*2],qz[30],x,y,lg[N*2+1],root1,dep[N*2];
long long ans;
string s;
void update(int x)
{
	for(int i=1;i<=23;++i)
		f[x][i]=f[f[x][i-1]][i-1];
}
int up(int x,int y)
{
	if(!y) return x;
	for(int i=lg[y];i>=0;i--) if(qz[i]<=y) x=f[x][i],y-=qz[i];
	return x;
}
int main()
{
	//freopen("1.in","r",stdin);
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	for (int i = 1; i <= N*2; i++)lg[i] = lg[i - 1] + (1 << lg[i - 1] == i);
	cin>>n>>s;
	for(i=1;i<=n;++i)
	{
		a[++a[0]]=s[i-1]-'0';
	}
	for(i=1;i<=n;++i)
	{
		a[++a[0]]=s[i-1]-'0';
	}
	
	qz[0]=1;
	for(i=1;i<=23;++i) qz[i]=qz[i-1]*2;
	root=0;num=0;
	for(i=1,l=1,r=0;i<=n*2;++i)
	{
		wz=root;
		if(!tree[wz][a[i]]){
			tree[wz][a[i]]=++num;
			f[num][0]=wz;
			update(num);
		}
		wz=tree[root][a[i]];
		if(i>r)
		{
			k=1;
			g[wz]++;
			g[f[wz][0]]--;
		}
		else
		{
			if(d[l+r-i]<=r-i+1)
			{
				k=d[l+r-i];
				x=pos[l+r-i];
				g[x]++;
				g[f[wz][0]]--;
				wz=x;
			}
			else
			{
				k=r-i+1;
				y=d[l+r-i]-(r-i+1);
				x=pos[l+r-i];
				x=up(x,y);
				g[x]++;
				g[f[wz][0]]--;
				wz=x;
			}	
		}
		
		while(1<=i-k&&i+k<=2*n&&a[i-k]==a[i+k]){
			if(!tree[wz][a[i+k]])
			{
				tree[wz][a[i+k]]=++num;
				f[num][0]=wz;
				update(num);
			}
			g[wz]--;
			g[tree[wz][a[i+k]]]++;
			wz=tree[wz][a[i+k]];
			k++;
		}
		pos[i]=wz;
		d[i]=k--;
		if(i+k>r){
			l=i-k;
			r=i+k;
		}
		if(i>n)
		{
		int len=0;
		if(i-d[i]+1<=n) len=i-n;
		else len=d[i];
		x=pos[i]; y=d[i]-len;
		x=up(x,y);
		g[x]--;
		}
	}
	
	root1=++num;
	for(i=1,l=1,r=0;i<=n*2;++i)
	{
		wz=root1;
		if(i>r) k=0;
		else
		{
			if(d[l+r-i+1]<=r-i+1)
			{
				k=d[l+r-i+1];
				x=pos[l+r-i+1];
				g[x]++;
				g[root1]--;
				wz=x;
			}
			else
			{
				k=r-i+1;
				y=d[l+r-i+1]-(r-i+1);
				x=pos[l+r-i+1];
				x=up(x,y);
				g[x]++;
				g[root1]--;
				wz=x;
			}	
		}
		
		while(1<=i-k-1&&i+k<=2*n&&a[i-k-1]==a[i+k]){
			if(!tree[wz][a[i+k]])
			{
				tree[wz][a[i+k]]=++num;
				f[num][0]=wz;
				update(num);
			}
			g[wz]--;
			g[tree[wz][a[i+k]]]++;
			wz=tree[wz][a[i+k]];
			k++;
		}
		pos[i]=wz;
		d[i]=k--;
		if(i+k>r){
			l=i-k-1;
			r=i+k;
		}
		if(i>n)
		{
		int len=0;
		if(i-d[i]<=n) len=i-n-1;
		else len=d[i];
		x=pos[i]; y=d[i]-len;
		x=up(x,y);
		g[x]--;
		}
	}
	for(i=0;i<=num;i++) if(i!=0&&i!=root1) dep[i]=dep[f[i][0]]+1;
	for(i=root1-1;i>0;i--)
	{
		g[f[i][0]]+=g[i];
		if(dep[i]*2-1<=n) ans+=1ll*(dep[i]*2-1)*g[i]%mod*g[i]%mod;
		ans%=mod;
	}
	for(i=num;i>root1;i--)
	{
		g[f[i][0]]+=g[i];
		if(dep[i]*2<=n) ans+=1ll*(dep[i]*2)*g[i]%mod*g[i]%mod;
		ans%=mod; 
	}
	ans=(ans%mod+mod)%mod;
	cout<<ans<<endl;
}