package y1;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int X,Y;
		int N;
		int[] A = new int[80];
		X = s.nextInt();
		Y = s.nextInt();
		N = s.nextInt();
		for(int i=0;i<N;i++){
			A[i] = s.nextInt();
		}

		////

		boolean fail = false;

		for(int i=0;i<N-1;i++){
			double t = (double)A[i]/X;
			double yx = t*Y;
			if(yx > A[i+1]){
				fail=true;
			}
		}

		if(fail == true){
			System.out.println("NO");
		}else{
			System.out.println("YES");
		}

	}

}