#include<bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
	double x, y;
	cin >> x >> y;
	x = x / 3600. * 1000;
	y = y / 3600. * 1000;
	int n;
	cin >> n;
	vector<int> v(n);
	for(int i = 0; i < n; i++)cin >> v[i];
	
	bool ok = true;

	for(int i = 0; i < n - 1; i++){
		if(v[i + 1] / y < v[i] / x)ok = false;	
	}
	cout << (ok ? "yes" : "no") << endl;
}