root@e:/usr/bin# ls -l screen
-rwxr-sr-x 1 root utmp 434216 Feb  7  2016 screen
root@e:/usr/bin# sudo chmod 775 screen
root@e:/usr/bin# ls -l screen
-rwxrwxr-x 1 root utmp 434216 Feb  7  2016 screen
root@e:/usr/bin# sudo apt-get install --reinstall screen
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-4.4.0-65 linux-headers-4.4.0-65-generic
  linux-image-4.4.0-65-generic linux-image-extra-4.4.0-65-generic
  linux-signed-image-4.4.0-65-generic snap-confine
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 3 not upgraded.
Need to get 560 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 screen amd64 4.3.1-2build1 [560 kB]
Fetched 560 kB in 5s (94.2 kB/s)
(Reading database ... 351448 files and directories currently installed.)
Preparing to unpack .../screen_4.3.1-2build1_amd64.deb ...
Unpacking screen (4.3.1-2build1) over (4.3.1-2build1) ...
Processing triggers for systemd (229-4ubuntu16) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Processing triggers for install-info (6.1.0.dfsg.1-5) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up screen (4.3.1-2build1) ...
root@e:/usr/bin# ls -l screen
-rwxr-sr-x 1 root utmp 434216 Feb  7  2016 screen
root@e:/usr/bin#