#include <iostream>

using namespace std;

int main(void){
  double x,y;
  int n,a[100000];
  cin >> x >> y >> n;
  for(int i=0; i<n; i++) cin >> a[i];
  x = x * 1000 / 3600;
  y = y * 1000 / 3600;
  double t;
  bool answer = 0;
  for(int i=0; i<n-1; i++){
    t = a[i] / x;
    if((double)(a[i+1])<(y*t)) answer = 1;
  }
  if(answer) cout << "NO" << endl;
  else cout << "YES" << endl;
  return 0;
}