import java.util.*; @SuppressWarnings("unused") public class Main { private static void solve() { int n = ni(); int m = ni(); int k = ni(); char[] s = ns(); int mod = 998244353; long[][] dp = new long[m + 1][k + 1]; long ret = 0; int used = 0; for (int i = 0; i < m; i++) { for (int j = 0; j < k; j++) { dp[i + 1][j + 1] += dp[i][j] * (26 - j) % mod; dp[i + 1][j + 1] %= mod; dp[i + 1][j] += dp[i][j] * j % mod; dp[i + 1][j] %= mod; } dp[i + 1][k] += dp[i][k] * 26 % mod; dp[i + 1][k] %= mod; if (i < n) { int c = s[i] - 'a'; for (int d = 0; d < 26; d++) { if (d < c) { int cnt = Math.min(k, Integer.bitCount(used | (1 << d))); dp[i + 1][cnt] += 1; dp[i + 1][cnt] %= mod; } } used |= 1 << c; if (i < n - 1 && Integer.bitCount(used) >= k) { ret ++; ret %= mod; } } } //(a,a,a) 1 //(a,b,*) 26 k>=2 //(a,a,*) 25 k=2 //a for (int i = 1; i <= m; i++) { ret += dp[i][k]; ret %= mod; } // System.out.println(Arrays.deepToString(dp)); System.out.println(ret); } public static void main(String[] args) { new Thread(null, new Runnable() { @Override public void run() { long start = System.currentTimeMillis(); String debug = args.length > 0 ? args[0] : null; if (debug != null) { try { is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug)); } catch (Exception e) { throw new RuntimeException(e); } } reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768); solve(); out.flush(); tr((System.currentTimeMillis() - start) + "ms"); } }, "", 64000000).start(); } private static java.io.InputStream is = System.in; private static java.io.PrintWriter out = new java.io.PrintWriter(System.out); private static java.util.StringTokenizer tokenizer = null; private static java.io.BufferedReader reader; public static String next() { while (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new java.util.StringTokenizer(reader.readLine()); } catch (Exception e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } private static double nd() { return Double.parseDouble(next()); } private static long nl() { return Long.parseLong(next()); } private static int[] na(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = ni(); return a; } private static char[] ns() { return next().toCharArray(); } private static long[] nal(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nl(); return a; } private static int[][] ntable(int n, int m) { int[][] table = new int[n][m]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[i][j] = ni(); } } return table; } private static int[][] nlist(int n, int m) { int[][] table = new int[m][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[j][i] = ni(); } } return table; } private static int ni() { return Integer.parseInt(next()); } private static void tr(Object... o) { if (is != System.in) System.out.println(java.util.Arrays.deepToString(o)); } }