#include<iostream>
#include<string>

using namespace std;

#define NMAX 100000
int main(){

	double X,Y;
	double Xa;
	int N;
	double a;

	cin>>X>>Y;
	cin>>N;
	cin>>a;
	if(N!=1){
		for(int i=0;i<N-1;i++){
			Xa=a*Y/X;
			cin>>a;
			if(Xa>a){
				cout<<"NO"<<endl;
				return 0;
			}
		}
	}

	cout<<"YES"<<endl;
	return 0;
}