#include "bits/stdc++.h"

using namespace std;

using LL = long long int;
using LD = long double;

using pii = pair<int, int>;
using pll = pair<LL, LL>;
using pdd = pair<double, double>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<LL>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;

const int INF = (1 << 30) - 1;
const LL INF64 = ((LL)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 1, 0, -1, 0 };
const int dy[] = { 0, 1, 0, -1 };

int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
LL gcd(LL x, LL y) { return y ? gcd(y, x % y) : x; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	double x, y, n;
	cin >> x >> y >> n;

	vd a(n);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}

	for (int i = 0; i < n - 1; i++) {
		if (x * a[i + 1] < y * a[i]) {
			cout << "NO" << endl;
			return 0;
		}
	}

	cout << "YES" << endl;
	return 0;
}