#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string>
#include<iostream>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include <sstream>
#include<iomanip>
#include <ctype.h>
using namespace std;

//#include<bits/stdc++.h>


int main() {
	
	double a, b;
	cin >> a >> b;
	int n;
	cin >> n;
	vector<int>r;
	for (int i = 0; i < n; i++) {
		int t;
		cin >> t;
		r.push_back(t);
		if (!i)continue;
		if ((double)r[i - 1] / a > (double)r[i] / b) {
			cout << "NO" << endl; return 0;
		}
	}
	cout << "YES" << endl;
	return 0;
}