#include <iostream>
#include <vector>

using namespace std;

int main() {
	double x, y, n, a;
	vector<double> v;
	double xx, yy;
	double d = 0;
	double dv = 0;
	double t;
	bool flag = false;
	double sum = 0;

	cin >> x >> y >> n;

	dv = y - x;

	//xx = x * 1000.0 / 60.0 / 60.0;
	//yy = y * 1000.0 / 60.0 / 60.0;

	//dv = yy - xx;

	for (int i = 0; i < n; i++) {
		cin >> a;
		v.push_back(a);
	}

	for (int i = 0; i < n - 1; i++) {
		for (int j = 0; j <= i; j++) {
			sum += v[j] / 1000;
		}

		t = sum / x;

		d = dv * t;

		if (d > v[i + 1] / 1000) {
			cout << "NO" << endl;
			flag = true;
			break;
		}

		sum = 0;
	}

	if (flag == false) {
		cout << "YES" << endl;
	}
}