why didnt i use semaphore ??

main.c

@@ -85,13 +85,17 @@ void truck_routine() {
         for(int i = 0; i < S; i++){
             pthread_mutex_lock(&sites[i].site_mutex);
             while(truck > 0 && sites[i].available_bikes < 2) {
+                sem_wait(&sites[i].sem_slots);
                 truck--;
                 sites[i].available_bikes++;
+                sem_post(&sites[i].sem_bikes);
                 printf("(TRUCK) Truck refilling site %d (%d bikes remaining)\n", i, sites[i].available_bikes);
             }
             while(truck < MAX_BIKES_TRUCK && sites[i].available_bikes > N-2) {
+                sem_wait(&sites[i].sem_bikes);
                 sites[i].available_bikes--;
                 truck++;
+                sem_post(&sites[i].sem_slots);
                 printf("(TRUCK) Truck taking bike from site %d (%d bikes remaining)\n", i, sites[i].available_bikes);
             }
             pthread_mutex_unlock(&sites[i].site_mutex);