#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "math.h"
#include "utility"
#include "string"
#include "map"
#include "unordered_map"
#include "iomanip"
#include "random"

using namespace std;
const long long int MOD = 1000000007;

long double X, Y, N;
long double num[100000];

int main() {
	ios::sync_with_stdio(false);
	cin >> X >> Y >> N;
	for (int i = 1; i <= N; i++)cin >> num[i];
	for (int i = 1; i < N; i++) {
		if (num[i + 1] / Y < num[i] / X) {
			cout << "NO\n";
			return 0;
		}
	}
	cout << "YES\n";
	return 0;
}