#include <stdio.h>

int main(int argc, char const *argv[]) {
  int x=0,y=0,n=0,temp=0; // X < Y
  scanf("%d %d\n%d",&x,&y,&n);
  int a[n];
  for (size_t i = 0; i < n; i++) {
    scanf("%d",&a[i]);
  }
  for (size_t i = 1; i < n; i++) {
    if(x*(a[i] / y) < a[i-1]){
      printf("NO\n");
      break;
    }else{
      temp++;
    }
  }
  if(temp==n){
  printf("YES\n");
  return 0;
  }
}