/usr/share/doc/libboost-doc/examples is in libboost1.65-doc 1.65.1+dfsg-0ubuntu5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libboost-doc/../libboost1.65-doc/examples
/usr/share/doc/libboost-doc/../libboost1.65-doc/examples