Write a program. You have been hired as a programmer and a Unix administrator asked you to check these three lists of users to find who had logged into all Unix servers and who had logged only into Unix server I. Here are the lists: Server I: alex linda kyrill akhmed sandra Server II: maya mila andrew rosa linda Server III: akhmed kyrill linda maya alex You need to write a program that takes all these user data as three files named server1.txt, server2.txt, server3.txt and outputs names of the users who had logged into all Unix servers and the users who had logged only into Unix server 1.