#include <bits/stdc++.h>
#include <bits/stdc++.h>
#include <bits/stdc++.h>
using namespace std;
#include <atcoder/modint>
using namespace atcoder;
using mint = modint998244353;
using ll = long long;
#define fix(x) fixed << setprecision(x)
#define rep(i, n) for(int i = 0; i < n; ++i)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);
const int MAX_N = 300300;
vector<ll> fac(MAX_N), finv(MAX_N), inv(MAX_N);
void init(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i=2;i<MAX_N;++i){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll mcomb(int n,int k){
    if (n<k) return 0;
    if (n<0 || k<0) return 0;
    return fac[n] * (finv[k] * finv[n-k] % MOD) % MOD;
}
ll mperm(int n,int k){
    if (n<k) return 0;
    if (n<0 || k<0) return 0;
    return fac[n] * finv[n-k] % MOD;
}
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    init();
    int n;
    string s;
    cin >> n >> s;
    if(s[0]==s[1]){
        mint ans = 0;
        rep(i,n/2+1) ans += mcomb(n/2,i) * mcomb(n/2,i);
        cout << ans.val() << '\n';
    }else{
        mint x = 2;
        cout << x.pow(n/2).val() << '\n';
    }
    return 0;
}