import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        double x = sc.nextInt();
        double y = sc.nextInt();
        int n = sc.nextInt();
        int[] points = new int[n];
        for (int i = 0; i < n; i++) {
            points[i] = sc.nextInt();
        }
        for (int i = 1; i < n; i++) {
            if (points[i - 1] / x > points[i] / y) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}