#include<string>
#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;
typedef long long int llint;
#define pub push_back
#define mp make_pair
#define fir first
#define sec second
const int big=((llint)1<<30);
const llint mod=1000000007;
//aabbaabb

//
int main(void){
	llint x,y,n,i,q;
	vector<llint> a;
	string ans="YES";
	cin>>x>>y>>n;
	a.resize(n);
	for(i=0;i<n;i++){cin>>a[i];}
	for(i=0;i<n-1;i++){if(y*a[i]>x*a[i+1]){ ans="NO";break; }}
	cout<<ans<<endl;
	return 0;
}