/usr/include/ImageMagick-6/ is in libmagick++-6-headers 8:6.8.9.9-7ubuntu5.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ImageMagick-6/Magick++/
/usr/include/ImageMagick-6/Magick++.h
/usr/include/ImageMagick-6/Magick++/Blob.h
/usr/include/ImageMagick-6/Magick++/ChannelMoments.h
/usr/include/ImageMagick-6/Magick++/CoderInfo.h
/usr/include/ImageMagick-6/Magick++/Color.h
/usr/include/ImageMagick-6/Magick++/Drawable.h
/usr/include/ImageMagick-6/Magick++/Exception.h
/usr/include/ImageMagick-6/Magick++/Functions.h
/usr/include/ImageMagick-6/Magick++/Geometry.h
/usr/include/ImageMagick-6/Magick++/Image.h
/usr/include/ImageMagick-6/Magick++/Include.h
/usr/include/ImageMagick-6/Magick++/Montage.h
/usr/include/ImageMagick-6/Magick++/Pixels.h
/usr/include/ImageMagick-6/Magick++/ResourceLimits.h
/usr/include/ImageMagick-6/Magick++/STL.h
/usr/include/ImageMagick-6/Magick++/TypeMetric.h