#include <bits/stdc++.h>

using namespace std;

#define INF 2000000000
#define MOD 1000000007
typedef long long ll;
typedef pair<int, int> P;


int main()
{
	double x, y;
	cin >> x >> y;
	int n;
	cin >> n;

	double ratio = y/x;

	double a[n];
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		if (i==0) {
			continue;
		}
		if (ratio>(a[i]/a[i-1])) {
			cout << "NO" << "\n";
			return 0;

		}
		cout << "YES" << "\n";
		return 0;
	}


	// for (int i = 0; i < n-1; i++) {
	// 	double t = a[i]/x;
	// 	cerr << "d_t: " << t << " " << t*y << endl;
	// 	double shisyo = t * y;
	// 	if (shisyo>a[i+1]) {
	// 		cout << "NO" << "\n";
	// 		return 0;
	// 	}
	// }
	// cout << "YES" << "\n";
	// return 0;
}