#include <bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
#define MOD 1000000007
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3f
#define EPS (1e-10)
using namespace std;
typedef long long ll;
typedef pair<int,int>P;

int a[200];
signed main(){
	int x,y,n;cin>>x>>y>>n;
	rep(i,n)cin>>a[i];
	rep(i,n-1){
		if(a[i+1]/(double)y<a[i]/(double)x){
			puts("NO");return 0;
		}
	}
	puts("YES");
}