using System;
using System.Linq;

class No512
{
    static void Main()
    {
        var speed = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();
        var count = Int32.Parse(Console.ReadLine());
        var distance = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();
        var ans = "YES";
        for (int i = 1; i < count; ++i)
        {
            if (distance[i - 1] * 1000 / speed[0] > distance[i] * 1000 / speed[1])
            {
                ans = "NO";
                break;
            }
        }
        Console.WriteLine(ans);
    }
}