#include<stdio.h>
int main()
{
	int kobaSpeed, masterSpeed;
	scanf("%d %d", &kobaSpeed, &masterSpeed);
	int inter;
	scanf("%d", &inter);
	int interLoc[inter];
	for (int i = 0; i < inter; i++){
		scanf("%d", &interLoc[i]);
	}
	for (int i = 0; i < inter - 1; i++)
	{
		if (masterSpeed * interLoc[i] > kobaSpeed * interLoc[i + 1])
		{
			printf("NO\n");
			return 0;
		}
	}
	printf("YES\n");
	return 0;
}