Your computer is really busy today and has no time to lose with basic and long computing. Create a thread that will launch the function long_computing() for you. Then wait for him to finish the work and get the output. If the return code is not satisfying, launch another thread to compute the function backup_computing(). This function will do the work. You can only use these functions : pthread_create(3) and pthread_join(3).

/*
* Function used to launch threads that will do the work for us.
*
* @long_computing : a function that will do a really long computing and that must be started by the thread.
*                 This function initially returns a pointer to an int and takes as argument a string.
*                 These have been casted into void* to match pthread_create() function specifications.
*                 You have to launch this function with the argument *string* and compare the returned value
*                 to *ret_value*. If the return value doesn't match *ret_value*,
*                 you have to launch another thread on the same argument with the function *backup_computing*.
*
* @backup_computing :  a backup function that must be used if the first thread didn't do the job correctly.
*                    As for *long_computing*, this function initially takes a string as argument and returns
*                    a pointer to an int.
*
* @string : the string that must be used as a parameter to both functions described above.
*
* @ret_value : the value to which the first returned code must be compared to to know if the first thread
*             correctly did the job or not.
*
* @return the int returned by the function started by the thread if no problem
*         -1 if you can't create the first thread
*         -2 if you can't join the first thread
*         -3 if you can't create the second thread
*         -4 if you can't join the second thread
*/
int doMyWork(void* long_computing(void*), void* backup_computing(void*), char* string, int ret_value){