void unreg_student(slist *students, int id, int number){
	clist * tempc;
	slist * temps;

	for (;students->info->id!=id;students=students->next);
	tempc=students->info->courses;
	for (;tempc->info->number!=number;tempc=tempc->next);
	temps=tempc->info->students;
	for (;temps->info->id!=id;temps=temps->next);
	tempc->info->students= remove_from_list_s(tempc->info->students,temps);
	students->info->courses= remove_from_list_c(students->info->courses,tempc);
}