using System;
using System.Linq;

namespace No._512
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] lines = Console.ReadLine().Split();
            float X = float.Parse(lines[0]);
            float Y = float.Parse(lines[1]);
            int N = int.Parse(Console.ReadLine());
            int[] A = Console.ReadLine().Trim().Split(' ').Select(x => int.Parse(x)).ToArray();

            X = X * 1000 / 3600;
            Y = Y * 1000 / 3600;

            for (int i = 0; i < N - 1; i++)
            {
                float buff = A[i] / X * Y;

                if (buff > A[i + 1])
                {
                    Console.WriteLine("NO");
                    return;
                }
            }

            Console.WriteLine("YES");
        }
    }
}