#include <iostream>
using namespace std;

int main() {
  int x, y, n;
  cin >> x >> y >> n;

  double dif=(double)y/x;
  int a[n], flg=1;
  cin >> a[0];

  for (int i=1; i<n; i++) {
    cin >> a[i];

    if (a[i-1]*dif-1e-9>a[i]) {
      flg=0;
    } 
  }

  cout << (flg ? "YES": "NO") << endl;
}