using System;

class Program
{
    private static readonly Scanner sc = new Scanner();
    static void Main(string[] args)
    {
        int x = sc.Int;
        int y = sc.Int;
        int n = sc.Int;
        int[] an = new int[n];
        for (int i = 0; i < n; i++)
            an[i] = sc.Int;

        for (int i = 0; i < n-1; i++)
        {
            if ((double)y * an[i] / x > an[i+1])
            {
                Console.WriteLine("NO");
                return;
            }
        }
        Console.WriteLine("YES");
    }
}

class Scanner
{
    private string[] _str = new string[0];
    private int _i;

    public string Str
    {
        get
        {
            if (_i >= _str.Length)
            {
                _str = Console.ReadLine().Split(' ');
                _i = 0;
            }
            return _str[_i++];
        }
    }

    public int Int { get { return int.Parse(Str); } }
    public long Long { get { return long.Parse(Str); } }
    public double Double { get { return double.Parse(Str); } }
}