#include<stdio.h>

int main(int argc, char const *argv[]){
	double x,y,a[80];
	int n,i;
	scanf("%f %f",&x,&y);
	scanf("%d",&n);
	for(i=0;i<n;i++){
		scanf("%f",&a[i]);
		if(i>0){
			if(a[i-1]*y/x>a[i]){
				printf("NO\n");
				return 0;
			}
		}
	}
	printf("YES\n");
	return 0;
}