using System;
using System.Linq;

class Solution
{
    static void Main(string[] args)
    {
        var vals = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        int x = vals[0];
        int y = vals[1];

        int n = int.Parse(Console.ReadLine());
        var a = new int[n];
        for (int i = 0; i < n; i++)
        {
            a[i] = int.Parse(Console.ReadLine());
        }

        bool lost = false;
        for (int i = 1; i < n; i++)
        {
            a[i] += a[i - 1];

            var xPos = a[i - 1];
            var t = xPos / x;
            var yPos = y * t;

            if (yPos > a[i])
            {
                lost = true;
            }
        }

        Console.WriteLine(lost ? "YES" : "No");
    }
}