description: You are given a binary string (i. e. a string consisting of characters 0 and/or 1) s of length n. You can perform the following operation with the string s at most once: choose a substring (a contiguous subsequence) of s having exactly k characters 1 in it, and shuffle it (reorder the characters in the substring as you wish).
  
  Calculate the number of different strings which can be obtained from s by performing this operation at most once.
  
  Input
  
  The first line contains two integers n and k (2 ≤ n ≤ 5000; 0 ≤ k ≤ n).
  
  The second line contains the string s of length n, consisting of characters 0 and/or 1.
  
  Output
  
  Print one integer — the number of different strings which can be obtained from s by performing the described operation at most once. Since the answer can be large, output it modulo 998244353.
  
  Examples
  
  Input
  
  
  7 2
  1100110
  
  
  Output
  
  
  16
  
  
  Input
  
  
  5 0
  10010
  
  
  Output
  
  
  1
  
  
  Input
  
  
  8 1
  10001000
  
  
  Output
  
  
  10
  
  
  Input
  
  
  10 8
  0010011000
  
  
  Output
  
  
  1
  
  Note
  
  Some strings you can obtain in the first example:
  
    * to obtain 0110110, you can take the substring from the 1-st character to the 4-th character, which is 1100, and reorder its characters to get 0110; 
    * to obtain 1111000, you can take the substring from the 3-rd character to the 7-th character, which is 00110, and reorder its characters to get 11000; 
    * to obtain 1100101, you can take the substring from the 5-th character to the 7-th character, which is 110, and reorder its characters to get 101. 
  
  
  
  In the second example, k = 0 so you can only choose the substrings consisting only of 0 characters. Reordering them doesn't change the string at all, so the only string you can obtain is 10010.
solution: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.io.OutputStream;
  import java.io.Writer;
  import java.io.IOException;
  import java.util.InputMismatchException;
  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author Nipuna Samarasekara
   */
  public class Main {
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          FastScanner in = new FastScanner(inputStream);
          FastPrinter out = new FastPrinter(outputStream);
          TaskD solver = new TaskD();
          solver.solve(1, in, out);
          out.close();
      }
  
      static class TaskD {
          public void solve(int testNumber, FastScanner in, FastPrinter out) {
              int n = in.nextInt(), k = in.nextInt();
              long mod = 998244353;
              long[][] ncr = IntegerUtils.generateBinomialCoefficients(n + 1, mod);
  
              String s = in.next();
              int ct = 0;
              for (int i = 0; i < n; i++) {
                  if (s.charAt(i) == '1') {
                      ct++;
                  }
  
              }
  
              int[] a = new int[ct + 2];
              int pos = 0;
              a[pos] = -1;
              pos++;
              for (int i = 0; i < n; i++) {
                  if (s.charAt(i) == '1') {
                      a[pos] = i;
                      pos++;
                  }
              }
              a[pos] = n;
              long ans = 0;
              if (ct < k || k == 0) {
                  ans = 1;
              } else if (ct == k) {
                  ans = ncr[n][ct];
              } else {
                  int st = 0, en = k + 1;
                  while (en < a.length) {
                      int len = a[en] - a[st] - 1;
                      ans += ncr[len][k];
                      //                System.out.println(ncr[len][k]);
                      if (ans >= mod) {
                          ans %= mod;
                      }
                      if (st > 0) {
                          int len2 = a[en - 1] - a[st] - 1;
                          ans -= ncr[len2][k - 1];
                          //                    System.out.println("-" + ncr[len2][k-1]);
                          ans %= mod;
                          if (ans < 0) {
                              ans += mod;
                          }
  
                      }
  
                      st++;
                      en++;
                  }
              }
  
              ans %= mod;
              out.println(ans);
  
  
          }
  
      }
  
      static class IntegerUtils {
          public static long[][] generateBinomialCoefficients(int n, long module) {
              long[][] result = new long[n + 1][n + 1];
              if (module == 1) {
                  return result;
              }
              for (int i = 0; i <= n; i++) {
                  result[i][0] = 1;
                  for (int j = 1; j <= i; j++) {
                      result[i][j] = result[i - 1][j - 1] + result[i - 1][j];
                      if (result[i][j] >= module) {
                          result[i][j] -= module;
                      }
                  }
              }
              return result;
          }
  
      }
  
      static class FastPrinter extends PrintWriter {
          public FastPrinter(OutputStream out) {
              super(out);
          }
  
          public FastPrinter(Writer out) {
              super(out);
          }
  
      }
  
      static class FastScanner extends BufferedReader {
          public FastScanner(InputStream is) {
              super(new InputStreamReader(is));
          }
  
          public int read() {
              try {
                  int ret = super.read();
                  //            if (isEOF && ret < 0) {
                  //                throw new InputMismatchException();
                  //            }
                  //            isEOF = ret == -1;
                  return ret;
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
          }
  
          public String next() {
              StringBuilder sb = new StringBuilder();
              int c = read();
              while (isWhiteSpace(c)) {
                  c = read();
              }
              if (c < 0) {
                  return null;
              }
              while (c >= 0 && !isWhiteSpace(c)) {
                  sb.appendCodePoint(c);
                  c = read();
              }
              return sb.toString();
          }
  
          static boolean isWhiteSpace(int c) {
              return c >= 0 && c <= 32;
          }
  
          public int nextInt() {
              int c = read();
              while (isWhiteSpace(c)) {
                  c = read();
              }
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              int ret = 0;
              while (c >= 0 && !isWhiteSpace(c)) {
                  if (c < '0' || c > '9') {
                      throw new NumberFormatException("digit expected " + (char) c + " found");
                  }
                  ret = ret * 10 + c - '0';
                  c = read();
              }
              return ret * sgn;
          }
  
          public String readLine() {
              try {
                  return super.readLine();
              } catch (IOException e) {
                  return null;
              }
          }
  
      }
  }
  
  