import java.util.Arrays;
import java.util.Scanner;
import java.util.concurrent.SynchronousQueue;

class Main {
	int N, M;
	int[] X, Y;

	public static void main(String[] args) {
		new Main().run();
	}

	void run() {
		Scanner sc = new Scanner(System.in);
		double X = sc.nextDouble();
		double Y = sc.nextDouble();
		int N = sc.nextInt();
		double[] A = new double[N];
		double[] tX = new double[N];
		double[] tY = new double[N];
		for (int i = 0; i < N; ++i) {
			A[i] = sc.nextDouble();
			tX[i] = A[i] / X;
			tY[i] = A[i] / Y;
		}
		boolean f = true;
		for (int i = 0; i + 1 < N; ++i) {
			if (tX[i] > tY[i + 1]) {
				f = false;
			}
		}
		if (f) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}