In member function 'void Vector3Array::input()',
    inlined from 'int main()' at /in/foo.cc:81:14:
/in/foo.cc:53:13: warning: 'arr.Vector3Array::arr' may be used uninitialized [-Wmaybe-uninitialized]
   53 |             arr[i]=Vector3(x,y,z);
      |             ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:80:18: note: 'arr' declared here
   80 |     Vector3Array arr(n);
      |                  ^~~