import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;

import static java.lang.System.in;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String[] inputs = reader.readLine().split(" ");
        int kobaSpeed = Integer.parseInt(inputs[0]);
        int masterSpeed = Integer.parseInt(inputs[1]);
        int N = Integer.parseInt(reader.readLine());
        int[] intersections = new int[N];
        inputs = reader.readLine().split(" ");
        for (int i = 0; i < N; i++) {
            intersections[i] = Integer.parseInt(inputs[i]);
        }

        String answer = "YES";
        for (int i = 0; i < N - 1; i++) {
            if (intersections[i+1] * kobaSpeed < intersections[i] * masterSpeed) {
                answer = "NO";
                break;
            }
        }
        System.out.println(answer);

    }
}