#include <iostream>

using namespace std;

int main(void){
  double x,y;
  int n;
  double a[81];
  cin >> x >> y >> n;
  for(int i=1; i<=n; i++) cin >> a[i];
  x = (x * 1000);
  y = (y * 1000);
  double t;
  bool answer = 0;
  for(int i=1; i<=n-1; i++){
    t = a[i] / x;
    if(a[i+1]<(y*t)){
      answer = 1;
      break;
    }
  }
  if(answer) cout << "NO" << endl;
  else cout << "YES" << endl;
  return 0;
}