Write a C program to control an escalator using threading and synchronization techniques. The escalator can move bidirectional from up to down or from down to up. If there is people going down, no one can use the escalator to go up and vice-versa unless the escalator is empty. Useful Libraries #include I #include #include #include #include #include #include Useful Functions int sem_init(sem_t *sem, int pshared, unsigned int value); int sem_wait(sem_t *sem); int sem_post(sem_t *sem); int pthread_mutex_init( pthread_mutex_t * mutex, const pthread_mutexattr_t * attr); int pthread_mutex_lock(pthread_mutex_t *mutex); int pthread_mutex_unlock(pthread_mutex_t *mutex); int pthread_create(pthread_t *thread, pthread_attr_t *attr, void *(*start_routine)(void *), void *arg); int pthread_join(pthread_t thread, void ** value _ptr); void pthread exit(void *value ptr)