Problem: One day Kefa found n baloons. For convenience, we denote color of i-th baloon as si — lowercase letter of the Latin alphabet. Also Kefa has k friends. Friend will be upset, If he get two baloons of the same color. Kefa want to give out all baloons to his friends. Help Kefa to find out, can he give out all his baloons, such that no one of his friens will be upset — print «YES», if he can, and «NO», otherwise. Note, that Kefa's friend will not upset, if he doesn't get baloons at all.

Input

The first line contains two integers n and k (1 ≤ n, k ≤ 100) — the number of baloons and friends.

Next line contains string s — colors of baloons.

Output

Answer to the task — «YES» or «NO» in a single line.

You can choose the case (lower or upper) for each letter arbitrary.

Examples

Input

4 2
aabb


Output

YES


Input

6 3
aacaab


Output

NO

Note

In the first sample Kefa can give 1-st and 3-rd baloon to the first friend, and 2-nd and 4-th to the second.

In the second sample Kefa needs to give to all his friends baloons of color a, but one baloon will stay, thats why answer is «NO».

Solution (in JAVA):

Solution:

		
		import java.awt.List;
		import java.io.*;
		import java.util.*;
		
		
		
		
		/*
		 * 
		 * daiict
		 *
		 * 
		 * 
		 */
		
		
		public class Main {
			FastScanner in;
			PrintWriter out;
		
			static ArrayList[] adj;
			static ArrayList[] obj;
			static int n;
			static int x;
			static int c;
			static int visited[];
			static int Ad[];
			static int Bd[];
			static double ans = 0;
			static int brr[][];
			static int a;
			static int b;
			static int parent[];
			static int size[];
			long mod = (long)1e9+7;
			static int ds[];
			
		//Segment tree do not delete
			static int arr[];	
			static int d[];
			static int h;
		// till now	
		
			class Segment{
			  private  int Lazy[];
			 
			    void ans(){
			   
			    	
			     int x = (int) (Math.ceil(Math.log(100000) / Math.log(2)));
			        int max_size = 2 * (int) Math.pow(2, x) - 1;
			        int SegTree[][] = new int[max_size][3]; // allocate memory
			        Lazy = new int[max_size];
			        
			       String s = in.next();
			       n = s.length();
			        
			        int q=in.nextInt();
			        
		
			        build_ST(0, 0, n - 1,SegTree,s);
			  
			        for(int i = 0;i<2*n;i++){
			        	System.out.println(SegTree[i][0] + " " + SegTree[i][1] + " " + SegTree[i][2] + " " + (i+n));
			        }
			        
			        while(q-->0)
			        {
			          int a = in.nextInt();
			          int b = in.nextInt();
			          
			          int d = getMaxST(0, n-1, a-1, b-1, 0,SegTree);
			          System.out.println(d);
			        }
			    }
			    
			    
			 void build_ST(int node, int start, int end,int SegTree[][],String s) 
			   {
			    if(start > end) return; 
			  	if(start == end) { 
			  		System.out.println(start + " " + node);
			  		if(s.charAt(start) == '('){
			  			SegTree[node][1] = 1;
			  		}else{
			  			SegTree[node][2] = 1;
			  		}
			  		
					return;
				}
				int mid=(start + end) >> 1;
				build_ST(node*2+1, start, mid, SegTree,s); // Init left child
				build_ST(node*2+2, 1+mid, end,SegTree,s); // Init right child
				
				// Init root value
				
				int t = Math.min(SegTree[2*node + 1][1], SegTree[2*node+2][2]);
				
				SegTree[node][0] = SegTree[2*node+1][0] + SegTree[2*node+2][0] + 2*t;
				SegTree[node][1] = SegTree[2*node+1][1] + SegTree[2*node+2][1] - t;
				SegTree[node][2] = SegTree[2*node+1][2] + SegTree[2*node+2][2] - t;
				
				
			}
		//	    void update_ST(int node, int start, int end, int l, int r, int diff) {
		//	        if(Lazy[node] != 0)
		//	        {
		//	            int pending = Lazy[node];
		//	            
		//	            SegTree[node] -= pending;
		//	            
		//	           if(start != end)
		//	            {
		//	                Lazy[2 * node + 1] += Lazy[node];
		//	                Lazy[2 * node + 2] += Lazy[node];
		//	            }
		//	           Lazy[node] = 0;
		//	        }
		//	        if (end < l || start > r)
		//	            return ;
		//	          if(l<=start && end<=r)
		//	        {
		//	        	  SegTree[node] -= diff;
		//	               
		//	            if(start != end) // not a leaf
		//	            {
		//	                Lazy[2*node+1] += diff;
		//	                Lazy[2*node+2] += diff;
		//	            }
		//	            return;
		//	        }
		//	        int mid=(start + end) >> 1;
		//		update_ST(node*2+1, start, mid, l, r, diff); // Updating left child
		//		update_ST(2+node*2, 1+mid, end, l, r, diff); // Updating right child
		//	
		//		SegTree[node] = Math.max(SegTree[node*2+1],SegTree[node*2+2]); 
		//		
		//	    }
			      int getMaxST(int start, int end, int l, int r, int node,int SegTree[][])
			    {
		//	    	  if(Lazy[node] != 0)
		//		        {
		//		            int pending = Lazy[node];
		//		            
		//		            SegTree[node] -= pending;
		//		            
		//		           if(start != end)
		//		            {
		//		                Lazy[2 * node + 1] += Lazy[node];
		//		                Lazy[2 * node + 2] += Lazy[node];
		//		            }
		//		           Lazy[node] = 0;
		//		        }
			        if (l <= start && r >= end)
			            return SegTree[node][0];
			         if (end < l || start > r)
			            return 0;
			        int mid = (start + end) >> 1;
			        return getMaxST(start, mid, l, r, 2 * node + 1,SegTree)+getMaxST(mid + 1, end, l, r, 2 * node + 2,SegTree);
			    }
			      
			}
			
			static class Pair implements Comparable<Pair>
		    {
				int x;int y;
				
		        Pair(int l, int m) {
		          
		        	this.x = l;
		            this.y = m;
		           
		        }
		        
		        public int compareTo(Pair p) {
		            if (this.x == p.x) {
		                return (int)(this.y-p.y);
		            }
		            return (int)(this.x - p.x);
		        }
		        
		        public String toString(){
		        	return x + " " + y;
		        }
		        
		        public boolean equals(Object o){
		        	if(o instanceof Pair){
		        		Pair a = (Pair)o;
		        		
		        		return this.x == a.x && this.y == a.y;
		        	}
		        	
		        	return false;
		        }
		        
		        public int hashCode(){
		        	return new Long(x).hashCode()*31 + new Long(y).hashCode();
		        }
		    
		    }
		    
			
			public static int gcd(int a, int b) {
				if (b == 0) return a;
				return gcd(b, a%b);
			}
			
			public static int find(int i){
				if(parent[i] != i){
					return find(parent[i]);
				}
				
				return i;
			}
			
			
			public static void union(int a,int b){
				int ra = find(a);
				int rb = find(b);
		
				if(ra!= rb){
					if(size[ra] > size[rb]){
						parent[rb] =ra;
						size[ra] += size[rb];
					}else{
						parent[ra] = rb;
						size[rb] += size[ra];
					}
				}
				
			}
		
			public static void apply(int p,int value){
				arr[p] += value;
				
				if(p < n){
					d[p] += value;
				}
			}
			
			public static void push(int p){
				
				for(int s = h;s>0;s--){
					int i = p >> s;
					
					if(d[i] != 0){
						apply(i<<1,d[i]);
						apply(i<<1|1,d[i]);
						d[i] = 0;
					}		
				}		
			}
			
			public static void lazybuild(int p){
				while(p > 1){
					p>>=1;
					arr[p] = Math.max(arr[p<<1], arr[p<<1|1]) + d[p];
				}
			}
			
			public static void lazyupdate(int l,int r,int value){
				l += n; r += n+1;		
				int l0 = l;int r0 = r;
				for(;l<r; l>>=1,r>>=1){
					if((l&1) == 1){
						apply(l++,value);
					}
					
					if((r&1) == 1){
						apply(--r,value);
					}
				}
				lazybuild(l0);
				lazybuild(r0-1);
					
			}
			
			public static int lazyquery(int l,int r){
				l += n;r += n+1;
				push(l);push(r-1);
				int res = (int)-2e9;
				
				for(;l<r;l>>=1,r>>=1){
					if((l&1) == 1){
						res = Math.max(arr[l++], res);
					}
					
					if((r&1) == 1){
						res = Math.max(arr[--r], res);
					}
				}
				
				return res;
			}
			
			public static void build(){
				
				for(int i = n-1;i>0;i--){
					arr[i] = Math.max(arr[i<<1], arr[i<<1|1]);
				}
				
			}
			
			public static void update(int p,int v){
				
				for(arr[p += n] = v; p>0; p>>=1 ){
					arr[p>>1] = Math.max(arr[p], arr[p^1]);
				}
				
			}
			
			public static int query(int l,int r){
				
				r++;
				int max = 0;
				for(l +=n,r +=n;l<r; l>>=1,r>>=1 ){
					
				
					
					if((l&1) == 1){
						max = Math.max(max, arr[l++]);
					}
					
					if((r&1) == 1){
						max = Math.max(max, arr[--r]);
					}
				}
				
				return max;
			}
			
			void multiply(long a[][], long b[][])
			{
			    
			    long mul[][] = new long[3][3];
			    for (int i = 0; i < 3; i++)
			    {
			        for (int j = 0; j < 3; j++)
			        {
			            mul[i][j] = 0;
			            for (int k = 0; k < 3; k++)
			                mul[i][j] = (int) ((mul[i][j] + (a[i][k]*b[k][j])%mod)%mod);
			        }
			    }
			 
			  
			    for (int i=0; i<3; i++)
			        for (int j=0; j<3; j++)
			            a[i][j] = mul[i][j];  
			}
			
			long power(long F[][], long n)
			{
			    long M[][] = {{1,1,0}, {1,0,0}, {0,1,0}};
			 
			    if (n==1)
			        return (long) ((F[0][0] + F[0][1])%mod);
			 
			    power(F, n/2);
			 
			    multiply(F, F);
			 
			    if (n%2 != 0)
			        multiply(F, M);
			 
			    return (long) ((F[0][0] + F[0][1])%mod) ;
			}
			 
			
			long findNthTerm(long n)
			{
			    long[][] F = {{1,1,0}, {1,0,0}, {0,1,0}} ;
			 
			    return power(F, n);
			}
			 
			
			
		    void solve() throws NumberFormatException, IOException {
		 
		    	Scanner in = new Scanner(System.in);
		    	
		    	int n = in.nextInt();
		    	int k = in.nextInt();
		    	in.nextLine();
		    	
		    	char arr[] = in.nextLine().toCharArray();
		    	
		    	int temp[] = new int[26];
		    	
		    	for(int i = 0;i<n;i++){
		    		temp[arr[i]-'a']++;
		    	}
		    	int f = 0;
		    	for(int i = 0;i<26;i++){
		    		if(temp[i] > k){
		    			f = 1;
		    			break;
		    		}
		    	}
		    	
		    	if(f == 0){
		    		System.out.println("YES");
		    	}else{
		    		System.out.println("NO");
		    	}
		
		   
		    	
		    	
		    	//System.out.println(ans);
		//    	Segment s = new S	egment();
		//    	
		//    	s.ans();
		    	
		//    	n = in.nextInt();
		//    	arr = new int[2*n];
		//    	d = new int[n];
		//    	h = (int)Math.ceil((Math.log(n)/Math.log(2)));
		//    	for(int i = 0;i<n;i++){
		//    		arr[i+n] = in.nextInt();
		//    	}
		//    	
		//    	build();
		    	
		    	 
		   // 	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		    
		    	 
		//    	 StringBuilder sb = new StringBuilder();
		// 
		//    	 int tests = Integer.parseInt(br.readLine().trim());
		//    	  
		//          while (tests-- > 0) {
		//        	 
		//        	
		//          }
		//          
		//          
		//          System.out.println(sb.toString());
		//          
		           
		         
		}
		
		    public static String[] reverse(String arr[]){
		    	
		    	
		    	for(int i = 0;i<arr.length/2;i++){
		    		String temp = arr[i];
		    		arr[i] = arr[arr.length-i-1];
		    		arr[arr.length-1-i] = temp;
		    	}
		    	
		    	return arr;
		    	
		    }
			
			
		    
		 
		    public static long sum(long x){
		    	return x<10?x:x%10 + sum(x/10);
		    }
			
			public static long gcd(long x, long y) {
				if (x == 0)
					return y;
				else
					return gcd( y % x,x);
			}
			static long inv(long x , long mod)
			{
				long r,y;
				for(r=1,y=mod-2;y!=0;x=x*x%mod,y>>=1)
				{
					if((y&1)==1)
						r=r*x%mod;
				
				}
				return r;
			}
			
			public static long pow(long x,long y,long n){
				if(y==0)
					return 1%n;
				if(y%2==0){
					long z=pow(x,y/2,n);
					return (z*z)%n;
				}
				return ((x%n)*pow(x,y-1,n))%n;
			}
			
			
			
			
			public static boolean isPrime(int n) {
				// Corner cases
				if (n <= 1)
					return false;
				if (n <= 3)
					return true;
		 
				// This is checked so that we can skip 
				// middle five numbers in below loop
				if (n % 2 == 0 || n % 3 == 0)
					return false;
		 
				for (int i = 5; i * i <= n; i = i + 6)
					if (n % i == 0 || n % (i + 2) == 0)
						return false;
		 
				return true;
			}
			
		
			void run() throws NumberFormatException, IOException {
				in = new FastScanner();
				out = new PrintWriter(System.out);
		
				solve();
		
				out.close();
			}
		
			class FastScanner {
				BufferedReader br;
				StringTokenizer st;
		
				public FastScanner() {
					br = new BufferedReader(new InputStreamReader(System.in));
				}
		
				String next() {
					while (st == null || !st.hasMoreTokens()) {
						try {
							st = new StringTokenizer(in.br.readLine());
						} catch (IOException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
					return st.nextToken();
				}
		
				int nextInt() {
					return Integer.parseInt(next());
				}
		
				long nextLong() {
					return Long.parseLong(next());
				}
		
				double nextDouble() {
					return Double.parseDouble(next());
				}
			}
			
			class Tri{
				
				Tri[] arr;
				
				public Tri(){
					arr = new Tri[27];
				}
				
			}
			
			
		 
		
			public static void main(String[] args) throws NumberFormatException, IOException {
				new Main().run();
			}
		}
		
		
		class Node{
			int a;
			int b;
			
		}
		
		class MyComp implements Comparator<Node>{
		    
			@Override
			public int compare(Node a,Node b) {
				
				// < == -1
				
				if(a.a < b.a){
					return -1;
				}else if(a.a > b.a){
					return 1;
				}else{
					return 0;
				}
				
				
			}
		}