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.
import java.util.*;
import java.io.*;
import java.lang.Math.*;

public class Graph {

	private int V;   // No. of vertices
	 
    // Array  of lists for Adjacency List Representation
    private LinkedList<Integer> adj[];
 
    // Constructor
    Graph(int v)
    {
        V = v;
        adj = new LinkedList[v];
        for (int i=0; i<v; ++i)
            adj[i] = new LinkedList();
    }
 
    //Function to add an edge into the graph
    void addEdge(int v, int w)
    {
        adj[v].add(w);
        adj[w].add(v);
        // Add w to v's list.
    }
 
    // A function used by DFS
    boolean DFSUtil(int v,boolean visited[],int a[])
    {
        // Mark the current node as visited and print it
        visited[v] = true;
        int key=a[v];
        //System.out.print(v+" ");
 
        // Recur for all the vertices adjacent to this vertex
        Iterator<Integer> i = adj[v].listIterator();
        while (i.hasNext())
        {
            int n = i.next();
            if (!visited[n])
                if(!DFSUtil(n, visited,a) || a[n]!=key)return false;
        }
        return true;
    }
 
    // The function to do DFS traversal. It uses recursive DFSUtil()
    boolean DFS(int v,int a[])
    {
        // Mark all the vertices as not visited(set as
        // false by default in java)
        boolean visited[] = new boolean[V];
        visited[v] = true;
        Iterator<Integer> i = adj[v].listIterator();
        while (i.hasNext())
        {
            int n = i.next();
            if(!DFSUtil(n, visited,a))
            {
            	return false;
            }
        }
        return true;
    }

	public static void main(String[] args) {

		InputReader in = new InputReader(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int n=in.nextInt();
		int a[]=new int[n];
		TreeSet<Integer> t=new TreeSet<Integer>();
		for (int i=0;i<n;i++)
		{
			a[i]=in.nextInt();		
			t.add(a[i]);
		}
		if(t.size()<=2)out.println("YES");
		else if(t.size()==3)
		{
			Iterator it=t.iterator();
			int x=(int)it.next();
			int b=(int)it.next();
			int c=(int)it.next();
			if(2*b==x+c)out.println("YES");
			else out.println("NO");
		}
		else out.println("NO");
		
		
		out.close();
	}

	static void swap(Pairs arr[], int i, int j) {
		Pairs t = arr[i];
		arr[i] = arr[j];
		arr[j] = t;
	}

	static int partition(Pairs arr[], int l, int h) {
		long x = arr[h].x;
		int i = (l - 1);

		for (int j = l; j <= h - 1; j++) {
			if (arr[j].x <= x) {
				i++;
				// swap arr[i] and arr[j]
				swap(arr, i, j);
			}
		}
		// swap arr[i+1] and arr[h]
		swap(arr, i + 1, h);
		return (i + 1);
	}

	// Sorts arr[l..h] using iterative QuickSort
	static void sort(Pairs arr[], int l, int h) {
		// create auxiliary stack
		int stack[] = new int[h - l + 1];

		// initialize top of stack
		int top = -1;

		// push initial values in the stack
		stack[++top] = l;
		stack[++top] = h;

		// keep popping elements until stack is not empty
		while (top >= 0) {
			// pop h and l
			h = stack[top--];
			l = stack[top--];

			// set pivot element at it's proper position
			int p = partition(arr, l, h);

			// If there are elements on left side of pivot,
			// then push left side to stack
			if (p - 1 > l) {
				stack[++top] = l;
				stack[++top] = p - 1;
			}

			// If there are elements on right side of pivot,
			// then push right side to stack
			if (p + 1 < h) {
				stack[++top] = p + 1;
				stack[++top] = h;
			}
		}
	}

	static class Pairs implements Comparable<Pairs> {
		long x;
		int y;

		Pairs(long a, int b) {
			x = a;
			y = b;
		}

		@Override
		public int compareTo(Pairs o) {
			// TODO Auto-generated method stub
			if (x == o.x)
				return Integer.compare(y, o.y);
			else
				return Long.compare(x, o.x);
		}

	}

	public static void debug(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public static boolean isPal(String s) {
		for (int i = 0, j = s.length() - 1; i <= j; i++, j--) {
			if (s.charAt(i) != s.charAt(j))
				return false;
		}
		return true;
	}

	public static String rev(String s) {
		StringBuilder sb = new StringBuilder(s);
		sb.reverse();
		return sb.toString();
	}

	public static long gcd(long x, long y) {
		if (y == 0)
			return x;
		if (x % y == 0)
			return y;
		else
			return gcd(y, x % y);
	}

	public static int gcd(int x, int y) {
		if (x % y == 0)
			return y;
		else
			return gcd(y, x % y);
	}

	public static long gcdExtended(long a, long b, long[] x) {

		if (a == 0) {
			x[0] = 0;
			x[1] = 1;
			return b;
		}
		long[] y = new long[2];
		long gcd = gcdExtended(b % a, a, y);

		x[0] = y[1] - (b / a) * y[0];
		x[1] = y[0];

		return gcd;
	}

	public static int abs(int a, int b) {
		return (int) Math.abs(a - b);
	}

	public static long abs(long a, long b) {
		return (long) Math.abs(a - b);
	}

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

	public static int min(int a, int b) {
		if (a > b)
			return b;
		else
			return a;
	}

	public static long max(long a, long b) {
		if (a > b)
			return a;
		else
			return b;
	}

	public static long min(long a, long b) {
		if (a > b)
			return b;
		else
			return a;
	}

	public static long[][] mul(long a[][], long b[][]) {
		long c[][] = new long[2][2];
		c[0][0] = a[0][0] * b[0][0] + a[0][1] * b[1][0];
		c[0][1] = a[0][0] * b[0][1] + a[0][1] * b[1][1];
		c[1][0] = a[1][0] * b[0][0] + a[1][1] * b[1][0];
		c[1][1] = a[1][0] * b[0][1] + a[1][1] * b[1][1];

		return c;
	}

	public static long[][] pow(long n[][], long p, long m) {
		long result[][] = new long[2][2];
		result[0][0] = 1;
		result[0][1] = 0;
		result[1][0] = 0;
		result[1][1] = 1;

		if (p == 0)
			return result;
		if (p == 1)
			return n;
		while (p != 0) {
			if (p % 2 == 1)
				result = mul(result, n);
			//System.out.println(result[0][0]);
			for (int i = 0; i < 2; i++) {
				for (int j = 0; j < 2; j++) {
					if (result[i][j] >= m)
						result[i][j] %= m;
				}
			}

			p >>= 1;
			n = mul(n, n);
			// System.out.println(1+" "+n[0][0]+" "+n[0][1]+" "+n[1][0]+" "+n[1][1]);
			for (int i = 0; i < 2; i++) {
				for (int j = 0; j < 2; j++) {
					if (n[i][j] >= m)
						n[i][j] %= m;
				}
			}
		}
		return result;
	}

	public static long pow(long n, long p) {
		long result = 1;
		if (p == 0)
			return 1;
		if (p == 1)
			return n;
		while (p != 0) {
			if (p % 2 == 1)
				result *= n;
			p >>= 1;
			n *= n;
		}
		return result;
	}

	static class InputReader {

		private final InputStream stream;
		private final byte[] buf = new byte[8192];
		private int curChar, snumChars;
		private SpaceCharFilter filter;

		public InputReader(InputStream stream) {
			this.stream = stream;
		}

		public int snext() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public int nextInt() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public long nextLong() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public int[] nextIntArray(int n) {
			int a[] = new int[n];
			for (int i = 0; i < n; i++) {
				a[i] = nextInt();
			}
			return a;
		}

		public long[] nextLongArray(int n) {
			long a[] = new long[n];
			for (int i = 0; i < n; i++) {
				a[i] = nextInt();
			}
			return a;
		}

		public String readString() {
			int c = snext();
			while (isSpaceChar(c)) {
				c = snext();
			}
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public String nextLine() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
}