#include <iostream>
using namespace std;

int main(){
	using ll = long long;
	ll x, y, n;
	cin >> x >> y >> n;
	ll a[n];
	for(int i = 0; i < n; i++) cin >> a[i];
	for(int i = 0; i < n - 1; i++){
		if(a[i + 1] - a[i] < 1. * y * a[i] / x - a[i]){
			cout << "NO" << endl;
			return 0;
		}
	}
	cout << "YES" << endl;
}