using System;
using System.IO;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Numerics;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using static System.Math;
using Debug = System.Diagnostics.Debug;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;


static class P
{
    static void Main()
    {
        var xy = Console.ReadLine().Split().Select(int.Parse).ToArray();
        double x = xy[0];
        double y = xy[1];
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split().Select(int.Parse).ToArray();
        for (int i = 0; i < n - 1; i++)
        {
            if (a[i] / x > a[i + 1] / y + 0.000001)
            {
                Console.WriteLine("NO");
                return;
            }
        }
        Console.WriteLine("YES");
    }
}