using System;
using System.Linq;

public class yukicoder
{
    public static void Main()
    {
		double[] speed = Console.ReadLine().Split(' ').Select(x => double.Parse(x)).ToArray();
		double a = speed[0];
		double b = speed[1];
		double len = double.Parse(Console.ReadLine());
		double[] cross = Console.ReadLine().Split(' ').Select(x => double.Parse(x)).ToArray();
		string answer = "YES";
		
		for(int i = 0; i < cross.Length - 1; i++)
		{
			if(cross[i] * b > cross[i + 1] * a)
			{
				answer = "NO";
				break;
			}
		}
		
		Console.WriteLine(answer);
    }
}