#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
using namespace std;
#define lint long long int
/*
vector<char>al(26);
al = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
vector<char>AL(26);
AL = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
*/


int main() {
	double X, Y, N;
	cin >> X >> Y >> N;
	vector<double>vec(N);
	for (int i = 0; i < N; i++) {
		cin >> vec[i];
	}
	int cnt = 0;
	for (int i = 0; i < N-1; i++) {
		if (vec[i] * Y > vec[i + 1]*X) {
			cnt++;
		}
	}
	if (cnt) {
		cout << "NO" << endl;
	}
	else {
		cout << "YES" << endl;
	}
}