Assignment name: limited_resources  
Expected files: limited_resources.c  
Allowed functions: memset, printf, malloc, free, write, pthread_create, pthread_detach,
pthread_join, pthread_mutex_init, pthread_mutex_destroy, pthread_mutex_lock,
pthread_mutex_unlock, usleep, gettimeofday
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Simulate a library with 3 computers shared among 10 students:
- Each student (thread) wants to use a computer for 2-5 seconds (random time)
- Only 3 students can use computers simultaneously
- Implement a "semaphore" using mutexes and a counter variable

Print when students:
- Arrive at the library
- Get a computer  
- Finish using the computer
- Leave the library

Usage: `./limited_resources`

Hint: Since POSIX semaphores are not allowed in the mandatory part,
implement your own semaphore with mutex + counter + condition logic.
This exercise simulates resource limitation like in Philosophers with forks.