import java.util.Scanner;
import java.util.TreeSet;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Main{
	static IntStream REPS(int v){return IntStream.range(0,v);}
	static IntStream REPS(int l,int r){return IntStream.rangeClosed(l,r);}
	static IntStream INS(int n) {return REPS(n).map(i->getInt());}
	static Scanner s=new Scanner(System.in);
	static int getInt(){return Integer.parseInt(s.next());}

	public static void main(String[]$){
		int x=getInt(),y=getInt();
		TreeSet<Integer> ts=INS(getInt()).boxed().collect(Collectors.toCollection(TreeSet::new));

		for(int i:ts) {
			if(ts.subSet((int)(i*1.0/y*x),false,i,true).size()>=2) {
				System.out.println("NO");
				return;
			}
		}
		System.out.println("YES");
	}
}