#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
int main() {
  double X,Y;
  int n,a[80];
  cin >> X >> Y >> n;
  for(int i=0; i<n; i++) {
      cin >> a[i];
  }
  for(int i=0; i<n-1; i++) {
      if(a[i]*Y/X>a[i+1]) {
          cout << "NO" << endl;
          return 0;
      }
  }
  cout << "YES" << endl;
}