#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(i=a;i<b;i++)
#define rloop(i,a,b) for(i=a;i>=b;i--)
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
const int inf=1000000001;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846

int main(){
	int x,y,i;
	cin>>x>>y;
	int n;
	cin>>n;
	vi a(n);
	loop(i,0,n){
		cin>>a[i];
	}
	loop(i,1,n){
		double l;
		l=x*a[i]/y;
		if(l<a[i-1]){
			cout<<"NO"<<endl;
			return 0;
		}
	}
	cout<<"YES"<<endl;
}