#include<bits/stdc++.h>
using namespace std;

int main(){
	cin.tie(0),ios::sync_with_stdio(false);
	int x,y,n;
	cin>>x>>y>>n;
	vector<int>a(n);
	for(auto&i:a)cin>>i;
	bool yes=true;
	for(int i=1;i<n;++i){
		if(a.at(i)<(long double)y*a.at(i-1)/x)yes=false;
	}
	if(yes)cout<<"YES\n"s;
	else cout<<"NO\n"s;
}