#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
using mint = modint998244353;
const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
mint dp[200005][2][2];//0:未満、aの出現
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	string s; cin >> s;
	dp[0][1][0] = 1;
	rep(i, n) {
		char c = s[i];
		int num = c - 'a';
		//0,0
		dp[i + 1][0][0] += dp[i][0][0] * 25;
		dp[i + 1][0][1] += dp[i][0][0];
		//0,1
		dp[i + 1][0][1] += dp[i][0][1] * 25;
		//1,0
		if ('a' == c) {
			dp[i + 1][1][1] += dp[i][1][0];
		}
		else {
			dp[i + 1][1][0] += dp[i][1][0];
			dp[i + 1][0][1] += dp[i][1][0];//a
			dp[i + 1][0][0] += dp[i][1][0] * (num - 1);//not a
		}
		//1,1
		if ('a' == c) {
			//nop
		}
		else {
			dp[i + 1][1][1] += dp[i][1][1];
			dp[i + 1][0][1] += dp[i][1][1] * (num - 1);//not a
		}
	}
	cout << dp[n][0][1].val() << endl;
	return 0;
}