import java.util.Scanner;

class no476{
	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		int n,a,x,i;
		long s=0;
		n=stdIn.nextInt();
		a=stdIn.nextInt();
		for(i=0;i<n;i++) {
			x=stdIn.nextInt();
			s+=x;
		}
		if(s%n==0&&s/n==a) System.out.print("YES");
		else System.out.print("NO");
	}
}