import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		char[] s = sc.next().toCharArray();
		sc.close();

		int mod = 998244353;
		long[] dp0 = new long[n + 1];
		long[] dp1 = new long[n + 1];
		long[] dp0a = new long[n + 1];
		long[] dp1a = new long[n + 1];
		dp0[0] = 1;
		for (int i = 0; i < n; i++) {
			int c = s[i] - 'a';
			if (c == 0) {
				dp0a[i + 1] += dp0[i];
			} else {
				dp0[i + 1] += dp0[i];
				dp0a[i + 1] += dp0a[i];
				dp1a[i + 1] += dp0[i];
				dp1a[i + 1] += dp0a[i] * (c - 1);
				dp1[i + 1] += dp0[i] * (c - 1);
			}
			dp1[i + 1] += dp1[i] * 25;
			dp1a[i + 1] += dp1[i];
			dp1a[i + 1] += dp1a[i] * 25;
			dp1[i + 1] %= mod;
			dp1a[i + 1] %= mod;
		}
		System.out.println(dp1a[n]);
	}
}