import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int X = scan.nextInt();
		int Y = scan.nextInt();
		int N = scan.nextInt();
		int []A = new int[N];
		for(int i = 0; i < N; i++) {
			A[i] = scan.nextInt();
		}
		scan.close();
		for(int i = 0; i < N - 1; i++) {
			double t = (double)A[i] / X;
			double l = (double)Y * t;

			if(l > A[i + 1]) {
				System.out.println("NO");
				System.exit(0);
			}
		}
		System.out.println("YES");

	}
}