using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace yukicoder_512 {
    class Program {
        static void Main(string[] args) {
            string[] s = Console.ReadLine().Split(' ');
            double x = double.Parse(s[0]);
            double y = double.Parse(s[1]);
            int n = int.Parse(Console.ReadLine());
            double[] a = new double[n];
            string[] t = Console.ReadLine().Split(' ');
            for(int i = 0; i < t.Length; i++) {
                a[i] = double.Parse(t[i]);
            }
            int judge = 0;
            for(int i = 1; i < t.Length; i++) {
                if (a[i] / y < a[i - 1] / x) judge++;
            }
            if (judge > 0) Console.WriteLine("NO");
            else Console.WriteLine("YES");
            Console.ReadLine();
        }
    }
}