#include <bits/stdc++.h>
using namespace std;

constexpr int mod = 998244353;
long long dp[200001][4];

int main() {
    int N;
    string S;
    cin >> N >> S;
    dp[0][0] = 1;
    for(int i = 0; i < N; i++) {
        for(int j = 0; j < 4; j++) {
            for(int k = 0; k < 26; k++) {
                if(k == 0) {
                    if(j == 0 || j == 2) {
                        if(j == 0 && S[i] == 'a') {
                            dp[i+1][1] += dp[i][j];
                            dp[i+1][1] %= mod;
                        }
                        else {
                            dp[i+1][j|3] += dp[i][j];
                            dp[i+1][j|3] %= mod;
                        }
                    }
                }
                else {
                    if(j >= 2) {
                        dp[i+1][j] += dp[i][j];
                        dp[i+1][j] %= mod;
                    }
                    else if(S[i]-'a' == k) {
                        dp[i+1][j] += dp[i][j];
                        dp[i+1][j] %= mod;
                    }
                    else if(S[i]-'a' > k) {
                        dp[i+1][j|2] += dp[i][j];
                        dp[i+1][j|2] %= mod;
                    }
                }
            }
        }
    }
    cout << dp[N][3] << endl;
}