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));
  }
}