Allowed functions:

#	Function	Description	Prototype
1	memset()	Fills the first 'n' bytes of the memory area pointed to by 's' with the constant byte 'c'.	void *ft_memset(void *s, int c, size_t n)
2	printf()	The functions printf() writes output to stdout, the standard output stream.	int printf(const char *restrict format, ...)
3	malloc()	The malloc() function allocates size bytes and returns a pointer to the allocated memory.	void *malloc(size_t size)
4	free()	The free() function frees the memory space pointed to by ptr, which must have been returned by a previous call to malloc()	void free(void *ptr)
5	usleep()	The usleep() function suspends execution of the calling thread for (at least) usec microseconds.	int usleep(useconds_t usec)
6	gettimeofday()	The function gettimeofday() can get the time as well as a timezone.	int gettimeofday(struct timeval *restrict tv, struct timezone *restrict tz)
7	pthread_create()	The pthread_create() function starts a new thread in the calling process. The new thread starts execution by invoking start_routine() arg is passed as the sole argument of start_routine().	int pthread_create(pthread_t *restrict thread, const pthread_attr_t *restrict attr, void *(*start_routine)(void *), void *restrict arg)
8	pthread_detach()	The pthread_detach() function marks the thread identified by thread as detached. When a detached thread terminates, its resources are automatically released back to the system without the need for another thread to join with the terminated thread.	int pthread_detach(pthread_t thread)
9	pthread_join()	The pthread_join() function waits for the thread specified by thread to terminate. If that thread has already terminated, then pthread_join() returns immediately. The thread pecified by thread must be joinable.	int pthread_join(pthread_t thread, void **retval)
10	pthread_mutex_init()	The pthread_mutex_init() initialize a mutex	int pthread_mutex_init(pthread_mutex_t *restrict mutex, const pthread_mutexattr_t *restrict attr) pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER
11	pthread_mutex_destroy()	The pthread_mutex_destroy() destroy a mutex	int pthread_mutex_destroy(pthread_mutex_t *mutex)
12	pthread_mutex_lock()	The mutex object referenced by mutex shall be locked by a call to pthread_mutex_lock() that returns zero or [EOWNERDEAD].	int pthread_mutex_lock(pthread_mutex_t *mutex)
13	pthread_mutex_lock()	The mutex object referenced by mutex shall be unlocked by a call to pthread_mutex_unlock() that returns zero or [EOWNERDEAD].	int pthread_mutex_lock(pthread_mutex_t *mutex)