#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------


int N;
string S;
ll dp[202020][2][2];
const ll mo=998244353;
void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>S;
	dp[0][0][0]=1;
	FOR(i,N) {
		int c=S[i];
		FOR(x,26) {
			if(x==0) {
				if(c=='a') {
					(dp[i+1][0][1]+=dp[i][0][0])%=mo;
					(dp[i+1][1][1]+=dp[i][1][0])%=mo;
				}
				else {
					(dp[i+1][1][1]+=dp[i][0][0])%=mo;
					(dp[i+1][1][1]+=dp[i][1][0])%=mo;
				}
			}
			else {
				if(x<c-'a') {
					(dp[i+1][1][0]+=dp[i][0][0])%=mo;
					(dp[i+1][1][1]+=dp[i][0][1])%=mo;
				}
				else if(x==c-'a') {
					(dp[i+1][0][0]+=dp[i][0][0])%=mo;
					(dp[i+1][0][1]+=dp[i][0][1])%=mo;
				}
				(dp[i+1][1][0]+=dp[i][1][0])%=mo;
				(dp[i+1][1][1]+=dp[i][1][1])%=mo;
			}
		}
	}
	
	cout<<dp[N][1][1]<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}