#include <cfloat>
#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	int X, Y, N;
	cin >> X >> Y >> N;
	int A[N];
	for (auto&& a : A) cin >> a;
	int V   = Y - X;
	int sum = 0;
	int i   = 0;
	for (auto&& a : A) {
		double ty = (double)(sum + a) / Y;
		if (sum > ty * X - DBL_MIN) {
			cout << "NO" << endl;
			return 0;
		}
		sum += a;
	}
	cout << "YES" << endl;
	return 0;
}