#include <bits/stdc++.h>
#include "bits/stdc++.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>
#include <stack>
#include <queue>
#include <cctype>
#include <stdio.h>
#include <map>
#include <unordered_map>
#include <string.h>
#include <utility>

typedef long long ll;
const int INF = 1e8;

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
using namespace std;

typedef pair<int, int> P;

int d[100];
int main() {

	int x,y;
	cin>>x>>y;



	/*cout<<rate<<endl;*/

	int n=0;
	cin>>n;

	int tmp=0;
	for(int i=0; i<n; i++){
		cin>>tmp;
		d[i] =tmp;
	}

	for(int i=0; i<n-1; i++){
		if(d[i]*y > d[i+1]*x){
		/*	cout<<d[i]*rate<<" "<<d[i+1]<<endl;*/
			cout<<"NO"<<endl;
			return 0;
		}
	}

	cout<<"YES"<<endl;

return 0;

}