class Pointer {
    std::vector<uint64_t> array;

public:
    explicit Pointer(int capacity) {
        array.reserve(capacity);
    }
};

   struct A (
     int x;
     int arr[];
   }
   struct A *a = malloc(sizeof(struct A)+ sizeof(int)*capacity);

#define MAX_ON_STACK 16
template<T>
class vector {
  int size;
  int capacity;
  bool useArrS;
  union {
      T arrS[MAX_ON_STACK];
      T *arr;
  }
  vector(int capacity) {
    useArrS = true;
    resize(capacity);    
  }

  void resize(int newCapacity) {
     if(capacity <= MAX_ON_STACK && useArrS) return;
     useArrS = false;
     T arrNew = new[newCapacity];
     copy(arr, arrNew, min(newCapacity, size));
     delete []arr;
     arr = newArr;
  }
  const T& at(int pos) {
    if (useArrS)
       return arrS[pos]; 
    else 
      return arr[pos];
  }
};