// #pragma GCC optimize(3)
#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using ld = long double;
using i128 = __int128_t;
using u128 = __uint128_t;
#define int long long
#define mem(a, b) memset((a), (b), sizeof(a))
#define all(a) (a).begin(), (a).end()
#define inf 0x3f3f3f3f
#define lowbit(x) (-x) & x
#define debug cout<<"$"
#define ls u << 1
#define rs u << 1 | 1
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
using pii = pair<int,int>;
mt19937 rnd(time(0));
const int MOD = 998244353;
const ld eps = 1;
int qmi(int m, int k){int res = 1, t = m;while (k){if (k & 1) res = (res * t) % MOD;t = t * t % MOD;k >>= 1;}return res;}
const int N = 1e7 + 7;
const int P = 13331;


struct mana
{
    char s[N];
    int k = 0;
    int d[N]; // 回文半径函数
    void init(string t)
    {
        int n = t.size()-1;
        s[0] = '$', s[++k] = '#';
        for (int i = 1; i <= n; i++)
            s[++k] = t[i], s[++k] = '#';
    }
    void get_d(){
    d[1]=1;
        for(int i=2,l,r=1;i<=k;i++){
            if(i<=r)d[i]=min(d[r-i+l],r-i+1);
            while(s[i-d[i]]==s[i+d[i]])d[i]++;
            if(i+d[i]-1>r)l=i-d[i]+1,r=i+d[i]-1;
        }  
    }
}man[2];
unordered_map<u64,u64> mb;
u64 h[N], p[N]; 
vector<unordered_map<u64,int>> id(N);
u64 get(int l, int r)
{
    return h[r] - h[l - 1] * p[r - l + 1];
}
void solve()
{
    int n;
    string s0;
    cin>>n>>s0;
    int t = n;
    man[1].init(" "+s0);
    s0 = " " + s0 + s0;
    man[0].init(s0);
    p[0] = 1;
    for (int i = 1; i <= 2*n; i ++ )
    {
        h[i] = h[i - 1] * P + s0[i];
        p[i] = p[i - 1] * P;
    }
    man[0].get_d(); 
    man[1].get_d(); 
    for(int q=0;q<2;q++)
    for (int i = 2; i <= man[q].k; i++)
    {
        int len;
        int l,r;
        if(i&1)
        {
            len = min(t/2*2,man[q].d[i]-1);
            l = i/2-(len/2-1);
            r = i/2+(len/2-1)+1;
        }
        else 
        {
            len = min(((t-1)/2*2+1),man[q].d[i]-1);
            l = i/2-len/2;
            r = i/2+len/2;
        }
        if(!len)    continue;
        auto z = get(l,r);
        // debug<<i<<"\n";
        // debug<<l<<" "<<r<<" "<<len<<" "<<q<<"\n";
        id[len][z] += (q?-1:1);
        while(!mb.count(z)&&l<=r)
        {
            l++,r--;
            auto t = get(l,r);
            mb[z] = t;
            z = t;
        }
    }   
    int ans = 0;
    for(int i=n;i;i--)
    {
        for(auto [c,d]:id[i])
        {
            ans += d*d%MOD*i%MOD;
            ans %= MOD;
            if(i>2)  id[i-2][mb[c]] += d;
        }
    }
    // while(ma.size())
    // {
    //     auto [c,d] = *ma.begin();
    //     ma.erase(ma.begin());
    //     auto [len,hash] = c;
    //     ans += (-len)*d%MOD*d%MOD;
    //     ans %= MOD;
    //     if(-len>=2)
    //         ma[{len+2,mb[hash]}]+=d;
    // }
    cout<<ans;
}   

signed main()
{
    // freopen("test.in","r",stdin);
    // freopen("test.out","w",stdout);
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    // cin>>T;
    while (T--)
        solve();
}
/*
6677667766776677
*/