Main.cc: In function ‘int main()’:
Main.cc:17:25: error: invalid use of member function ‘std::vector<_Tp, _Alloc>::size_type std::vector<_Tp, _Alloc>::size() const [with _Tp = int; _Alloc = std::allocator<int>; std::vector<_Tp, _Alloc>::size_type = long unsigned int]’ (did you forget the ‘()’ ?)
   17 |  for(int i = 0; i < arr.size; i++) {
      |                     ~~~~^~~~
      |                             ()