#include <iostream>
#include <vector>
#include <algorithm>
#include <stdio.h>

using namespace std;

typedef long long ll;

int main () {
    long double x , y;
   cin >> x >> y;
    int n;
    cin >> n;
    vector<long double> a(n + 1);
    for (int i = 1; i <= n; i++) {
       cin >> a[i];
    }
    long double pos = 0;
    for (int i = 1; i < n; i++) {
        pos += (a[i] - a[i - 1]) * y / x + 0.5;
        if (pos > a[i + 1]) {
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
    return 0;
}