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.*;
  import java.util.*;
  
  public class Main {
  	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  	static StringTokenizer st;
  	static PrintWriter pr = new PrintWriter(System.out);
  	static String readLine() throws IOException {
  		return br.readLine();
  	}
  	static String next() throws IOException {
  		while (st == null || !st.hasMoreTokens())
  			st = new StringTokenizer(readLine());
  		return st.nextToken();
  	}
  	static int readInt() throws IOException {
  		return Integer.parseInt(next());
  	}
  	static long readLong() throws IOException {
  		return Long.parseLong(next());
  	}
  	static double readDouble() throws IOException {
  		return Double.parseDouble(next());
  	}
  	static char readChar() throws IOException {
  		return next().charAt(0);
  	}
  	static class Pair implements Comparable<Pair> {
  		int f, s;
  		Pair(int f, int s) {
  			this.f = f;
  			this.s = s;
  		}
  		public int compareTo(Pair other) {
  			if (this.f != other.f) return this.f - other.f;
  			return this.s - other.s;
  		}
  	}
  	final static int mod = 998244353;
  	static long pow(long b, long p) {
  		long ret = 1;
  		while (p > 0) {
  			if ((p&1) == 1) ret = ret*b%mod;
  			b = b*b%mod;
  			p >>= 1;
  		}
  		return ret;
  	}
  	static long fac[], inv[];
  	static long C(int n, int k) {
  		return fac[n]*(inv[k]*inv[n - k]%mod)%mod;
  	}
  	static void solve() throws IOException {
  		int n = readInt(), k = readInt();
  		fac = new long[n + 1];
  		inv = new long[n + 1];
  		fac[0] = inv[0] = 1;
  		for (int i = 1; i <= n; ++i) {
  			fac[i] = fac[i - 1]*i%mod;
  			inv[i] = pow(fac[i], mod - 2);
  		}
  		String s = " " + readLine();
  		int tot = 0;
  		for (int i = 1; i <= n; ++i)
  			tot += s.charAt(i) - '0';
  		if (k == 0 || tot < k) {
  			pr.println(1);
  			return;
  		}
  		long ans = 1;
  		for (int L = 1; L <= n; ++L) {
  			int R = L - 1, cnt = 0;
  			while (R < n && cnt + s.charAt(R + 1) - '0' <= k) {
  				cnt += s.charAt(R + 1) - '0';
  				++R;
  			}
  			int num = R - L + 1;
  			if (cnt == 0 || cnt == num) continue;
  			long add = 0;
  			if (s.charAt(L) == '1') add = C(num - 1, cnt);
  			else add = C(num - 1, cnt - 1);
  			ans = (ans + add)%mod;
  		}
  		pr.println(ans);
  	}
  	public static void main(String[] args) throws IOException {
  		solve();
  		//for (int t = readInt(); t > 0; --t) solve();
  		pr.close();
  	}
  }
  