import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		double student = sc.nextDouble()*1000/3600;
		double teacher = sc.nextDouble()*1000/3600;
		int n = sc.nextInt();
		double[] intersection = new double[n];
		for (int i=0; i<n; i++) {
			intersection[i] = sc.nextInt();
		}
		
		boolean F = true;
		for (int i=0; i<n-1; i++) {
			if (intersection[i]*teacher < intersection[i+1]*student) {F = false;}
		}
		System.out.println(F==true?"YES":"NO");
	}
}