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 D{
  	static FastReader sc=null;
  	
  	public static void main(String[] args) {
  		sc=new FastReader();
  		precomp();
  		int n=sc.nextInt(),k=sc.nextInt();
  		int pre[]=new int[n+1];
  		char s[]=sc.next().toCharArray();
  		
  		int a[]=new int[n];
  		for(int i=0;i<n;i++)a[i]=(s[i]-'0');
  			
  		for(int i=0;i<n;i++)pre[i+1]=pre[i]+a[i];
  		
  		long ans=1;
  		
  		if(pre[n]<k) {
  			System.out.println(ans);
  			return;
  		}
  		
  		for(int i=0;i<n;i++) {
  			for(int j=i+1;j<n;j++) {
  				//change i and j first and shuffle the between characters
  				int ones=pre[j+1]-pre[i];
  				if(ones<=k) {
  					ones-=(a[i]^1);
  					ones-=(a[j]^1);
  					
  					long ways=NCK(j-i-1,ones);
  					ans=add(ans,ways);
  				}
  			}
  		}
  		
  		System.out.println(ans);
  	}
  	static long fac[];
  	static long invs[];
  	
  	static int nax=(int)1e4;
  	
  	static void precomp() {
  		fac=new long[nax];
  		invs=new long[nax];
  		
  		fac[0]=1;
  		invs[0]=1;
  		for(int i=1;i<nax;i++) {
  			fac[i]=mul(fac[i-1],i);
  			invs[i]=mul(invs[i-1],modInv(i));
  		}
  	}
  	static long NCK(int n,int k) {
  		if(n<k || k<0 || n<0)return 0;
  		
  		return mul(fac[n],mul(invs[k],invs[n-k]));
  	}
  	
  	static long sub(long a,long b) {
  		a-=b;
  		if(a<0)a+=mod;
  		return a;
  	}
  	static long add(long a,long b) {
  		a+=b;
  		if(a>=mod)a-=mod;
  		return a;
  	}
  	
  	static long mod=(long)998244353;
  	
  	static long mul(long a ,long b) {
  		return (a*b)%mod;
  	}
  
  	static long exp(long base,long e) {
  		if(e==0) return 1;
  		long half=exp(base,e/2);
  		if(e%2==0)return mul(half,half);
  		return mul(half,mul(half,base));
  	}
  	
  	static long modInv(long a) {
  		return exp(a,mod-2);
  	}
  
  	
  	static int[] ruffleSort(int a[]) {
  		ArrayList<Integer> al=new ArrayList<>();
  		for(int i:a)al.add(i);
  		Collections.sort(al);
  		for(int i=0;i<a.length;i++)a[i]=al.get(i);
  		return a;
  	}
  	
  	static void print(int a[]) {
  		for(int e:a) {
  			System.out.print(e+" ");
  		}
  		System.out.println();
  	}
  	
  	static class FastReader{
  		
  		StringTokenizer st=new StringTokenizer("");
  		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  		
  		String next() {
  			while(!st.hasMoreTokens()) 
  				try {
  					st=new StringTokenizer(br.readLine());
  				}
  			   catch(IOException e){
  				   e.printStackTrace();
  			   }
  			return st.nextToken();
  		}
  		
  		int nextInt() {
  			return Integer.parseInt(next());
  		}
  		
  		long nextLong() {
  			return Long.parseLong(next());
  		}
  		
  		int[] readArray(int n) {
  			int a[]=new int[n];
  			for(int i=0;i<n;i++)a[i]=sc.nextInt();
  			return a;
  		}
  	}
  	
  	
  }
  