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

signed main(){
	double x, y;
	cin >> x >> y;
	int n;
	cin >> n;
	vector<int> v(n);
	for(int i = 0; i < n; i++)cin >> v[i];
	
	bool ok = true;

	for(int i = 0; i < n - 1; i++){
		//printf("%.5f %.5f\n", (double)v[i + 1] / y, (double)v[i] / x);
		if((double)(v[i + 1] / y) < ((double)v[i] / x))ok = false;
	}
	cout << (ok ? "YES" : "NO") << endl;
}