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.io.*;
import java.util.*;

public class CODEFORCES
{
	private InputStream is;
	private PrintWriter out;
	int time = 0, val[][], dp[][], DP[], start[], end[], dist[], black[],
			MOD = (int) (1e9 + 7), arr[], weight[][], x[], y[], parent[];
	int MAX = 800000, N, K;
	long red[];
	ArrayList<Integer>[] amp;
	// boolean b[], boo[][];
	Pair prr[];
	HashSet<Integer> hs = new HashSet<>();
	long Dp[][][][] = new long[110][110][12][12];

	void soln() 
	{
		is = System.in;
		out = new PrintWriter(System.out);
		long s = System.currentTimeMillis();
		solve();
		// out.close();
		out.flush();
		/// tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception 
	{
		new Thread(null, new Runnable()
		{
			public void run() 
			{
				try 
				{

					// new CODEFORCES().soln();
				} catch (Exception e) 
				{
					System.out.println(e);
				}
			}
		}, "1", 1 << 26).start();
		new CODEFORCES().soln();
	}

	int a, b;
	int see[][] = new int[2050][2050];
	boolean bee[][] = new boolean[2050][2050];
	Queue<Pair> q = new LinkedList<>();
	void solve() 
	{
		int n = ni(), k = ni();
		String s = ns();
		int arr[] = new int[26];
		for(char ch : s.toCharArray()) arr[ch-'a']++;
		for(int i : arr) if(i>k) {System.out.println("NO");return ;}
		System.out.println("YES");
	}
	int min(int a, int b){
		if(a>b) return b;
		return a;
	}
	boolean check(int ans) {
		while (ans > 0) {
			int c = ans % 10;
			if (!(c == a || c == b))
				return false;
			ans /= 10;
		}
		return true;
	}

	long npr(long[] power, int n, int r) {
		if (r > n)
			return 0;
		return (((power[n] * power(power[r], MOD - 2, MOD)) % MOD) * power(
				power[n - r], MOD - 2, MOD)) % MOD;
	}

	class Pair implements Comparable<Pair> {
		int u, v, i;

		Pair(int u, int v) {
			this.u = u;
			this.v = v;
		}

		Pair(int u, int v, int i) {
			this.u = u;
			this.v = v;
			this.i = i;
		}

		public int hashCode() {
			return Objects.hash();
		}

		/*
		 * public boolean equals(Object o) { Pair other = (Pair) o; return ((u
		 * == other.u && v == other.v) || (v == other.u && u == other.v)); }
		 */
		public int compareTo(Pair other) {
			// return Integer.compare(val, other.val);
			return Long.compare(v, other.v) != 0 ? (Long.compare(v, other.v))
					: (Long.compare(u, other.u));
		}

		public String toString() {
			return this.u + " " + this.v;
		}
	}

	int max(int a, int b) {
		if (a > b)
			return a;
		return b;
	}

	void buildGraph(int n) {
		for (int i = 0; i < n; i++) {
			int x1 = ni() - 1, y1 = ni() - 1;
			amp[x1].add(y1);
			amp[y1].add(x1);
			x[i] = x1;
			y[i] = y1;
		}
	}

	long modInverse(long a, long mOD2) {
		return power(a, mOD2 - 2, mOD2);
	}

	long power(long x, long y, long m) {
		if (y == 0)
			return 1;
		long p = power(x, y / 2, m) % m;
		p = (p * p) % m;

		return (y % 2 == 0) ? p : (x * p) % m;
	}

	public long gcd(long a, long b) {
		if (b == 0)
			return a;
		return gcd(b, a % b);
	}

	static class ST1 {
		int arr[], st[], size;

		ST1(int a[]) {
			arr = a.clone();
			size = 10 * arr.length;
			st = new int[size];
			build(0, arr.length - 1, 1);
		}

		void build(int ss, int se, int si) {
			if (ss == se) {
				st[si] = arr[ss];
				return;
			}
			int mid = (ss + se) / 2;
			int val = 2 * si;
			build(ss, mid, val);
			build(mid + 1, se, val + 1);
			st[si] = Math.min(st[val], st[val + 1]);
		}

		int get(int ss, int se, int l, int r, int si) {
			if (l > se || r < ss || l > r)
				return Integer.MAX_VALUE;
			if (l <= ss && r >= se)
				return st[si];
			int mid = (ss + se) / 2;
			int val = 2 * si;
			return Math.min(get(ss, mid, l, r, val),
					get(mid + 1, se, l, r, val + 1));
		}
	}

	static class ST {
		int arr[], lazy[], n;

		ST(int a) {
			n = a;
			arr = new int[10 * n];
			lazy = new int[10 * n];
		}

		void up(int l, int r, int val) {
			update(0, n - 1, 0, l, r, val);
		}

		void update(int l, int r, int c, int x, int y, int val) {
			if (lazy[c] != 0) {
				lazy[2 * c + 1] += lazy[c];
				lazy[2 * c + 2] += lazy[c];
				if (l == r)
					arr[c] += lazy[c];
				lazy[c] = 0;
			}
			if (l > r || x > y || l > y || x > r)
				return;
			if (x <= l && y >= r) {
				lazy[c] += val;
				return;
			}
			int mid = l + r >> 1;
			update(l, mid, 2 * c + 1, x, y, val);
			update(mid + 1, r, 2 * c + 2, x, y, val);
			arr[c] = Math.max(arr[2 * c + 1], arr[2 * c + 2]);
		}

		int an(int ind) {
			return ans(0, n - 1, 0, ind);
		}

		int ans(int l, int r, int c, int ind) {
			if (lazy[c] != 0) {
				lazy[2 * c + 1] += lazy[c];
				lazy[2 * c + 2] += lazy[c];
				if (l == r)
					arr[c] += lazy[c];
				lazy[c] = 0;
			}
			if (l == r)
				return arr[c];
			int mid = l + r >> 1;
			if (mid >= ind)
				return ans(l, mid, 2 * c + 1, ind);
			return ans(mid + 1, r, 2 * c + 2, ind);
		}
	}

	public static int[] shuffle(int[] a, Random gen) {
		for (int i = 0, n = a.length; i < n; i++) {
			int ind = gen.nextInt(n - i) + i;
			int d = a[i];
			a[i] = a[ind];
			a[ind] = d;
		}
		return a;
	}

	long power(long x, long y, int mod) {
		long ans = 1;
		while (y > 0) {
			if (y % 2 == 0) {
				x = (x * x) % mod;
				y /= 2;
			} else {
				ans = (x * ans) % mod;
				y--;
			}
		}
		return ans;
	}

	// To Get Input
	// Some Buffer Methods
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
			// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n && !(isSpaceChar(b))) {
			buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;

	private void tr(Object... o) {
		if (!oj)
			System.out.println(Arrays.deepToString(o));
	}
}