#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <tuple>        //tuple
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits
#include <functional>

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	int X, Y, N;
	cin >> X >> Y >> N;

	int A1, A2;
	cin >> A1;

	double temp;

	for (int i = 0; i < N - 1; i++) {
		cin >> A2;
		temp = Y * A1 / (double)X;
		if (A2 < temp) {
			cout << "NO" << endl;
			return 0;
		}
		A1 = A2;
	}

	cout << "YES" << endl;

	return 0;

}