Today, hedgehog Filya went to school for the very first time! Teacher gave him a homework which Filya was unable to complete without your help.

Filya is given an array of non-negative integers a1, a2, ..., an. First, he pick an integer x and then he adds x to some elements of the array (no more than once), subtract x from some other elements (also, no more than once) and do no change other elements. He wants all elements of the array to be equal.

Now he wonders if it's possible to pick such integer x and change some elements of the array using this x in order to make all elements equal.

Input

The first line of the input contains an integer n (1 ≤ n ≤ 100 000) — the number of integers in the Filya's array. The second line contains n integers a1, a2, ..., an (0 ≤ ai ≤ 109) — elements of the array.

Output

If it's impossible to make all elements of the array equal using the process given in the problem statement, then print "NO" (without quotes) in the only line of the output. Otherwise print "YES" (without quotes).

Examples

Input

5
1 3 3 2 1


Output

YES


Input

5
1 2 3 4 5


Output

NO

Note

In the first sample Filya should select x = 1, then add it to the first and the last elements of the array and subtract from the second and the third elements.
/*
 * Remember a 6.0 student can know more than a 10.0 student.
 * Grades don't determine intelligence, they test obedience. 
 * I Never Give Up.
 * I will become Candidate Master.
 * I will defeat Saurabh Anand.
 * Skills are Cheap,Passion is Priceless.
 */
import java.util.*;
import java.util.Map.Entry;
import java.io.*;

import static java.lang.System.out;
import static java.util.Arrays.*;
import static java.lang.Math.*;
public class ContestMain {
	private static Reader in=new Reader();
	private static StringBuilder ans=new StringBuilder();
	private static long MOD=1000000000+7;//10^9+7
	private static final int N=100000+7; //10^5+7
//	private static final double EPS=1e-9;
//	private static final int LIM=26;
//	private static final double PI=3.1415;
	private static ArrayList<Integer> v[]=new ArrayList[N];
//	private static int color[]=new int[N];
	private static boolean mark[]=new boolean[N];
//	private static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
//	private static ArrayList<Pair> v[]=new ArrayList[N];
	private static long powmod(long x,long n){
		if(n==0||x==0)return 1;
		else if(n%2==0)return(powmod((x*x)%MOD,n/2));
		else return (x*(powmod((x*x)%MOD,(n-1)/2)))%MOD;
	}
	private static void shuffle(long [] arr) {
		for (int i = arr.length - 1; i >= 2; i--) {
			int x = new Random().nextInt(i - 1);
	        long temp = arr[x];
	        arr[x] = arr[i];
	        arr[i] = temp;
	    }
	 }
//	private static long gcd(long a, long b){
//		if(b==0)return a;
//		return gcd(b,a%b);
//	}
//	private static boolean check(int x,int y){
//		if((x>=0&&x<n)&&(y>=0&&y<m)&&mat[x][y]!='X'&&!visited[x][y])return true;
//		return false;
//	}
//	static class Node{
//		int left;
//		int right;
//		Node(){
//			left=0;
//			right=0;
//		}
//	}
	public static void main(String[] args) throws IOException{
		int n=in.nextInt();
		HashSet<Long> set=new HashSet();
		for(int i=0;i<n;i++)
			set.add(in.nextLong());
		long ar[]=new long[3];
		if(set.size()<=2)out.println("YES");
		else if(set.size()==3){
			int i=0;
			for(long a:set)
				ar[i++]=a;
			sort(ar);
			if(ar[1]-ar[0]==ar[2]-ar[1])out.println("YES");
			else out.println("NO");
		}
		else out.println("NO");
	}
	static class Pair<T> implements Comparable<Pair>{
		int l;
		int r;
		int ind;
		Pair(){
			l=0;
			r=0;
			ind=0;
		}
		Pair(int k,int v,int i){
			l=k;
			r=v;
			ind=i;
		}
//		@Override
//		public int compareTo(Pair o) {
//			if(o.l!=l)return (int) (l-o.l);
//			else return (int)(r-o.r);
//		}
		//Fenwick tree question comparator
		@Override
		public int compareTo(Pair o) {
			if(o.r!=r)return (int) (r-o.r);
			else return (int)(l-o.l);
		}
	}
	static class Reader{
        BufferedReader br;
        StringTokenizer st;
        public Reader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
 
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                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());
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}