import java.util.*;
import java.lang.*;
 
public class Main {
    public static void main(String[] args) {

        Scanner sc  = new Scanner(System.in); 

        int n = Integer.parseInt(sc.next());
        long a = Long.parseLong(sc.next());

        float ans = 0;
        
        long[] dim = new long[(int)n];
        for(int i=0;i<n;i++){
            dim[i] = Long.parseLong(sc.next());
        }
        Arrays.sort(dim);
        
        if(n%2==1){
            if(dim[n/2]==a) System.out.println("YES");
            else              System.out.println("NO");
                     //System.out.println(dim[n/2]);
        }else{
             if( ( dim[n/2] + dim[(n/2)+1] ) / 2 ==a) System.out.println("YES");
            else              System.out.println("NO");
        }
        
    


        System.out.println();
    }

}