penniisss

 for(int i = 0; i < NUMBER_OF_THREADS; i++){
   pthread_mutex_lock(&lock);
    if(pthread_join(tid[i],(void **) &value[i]) == 0){
        sum = sum + value[i]; //add four sums together
    }
    else{
      pthread_mutex_unlock(&lock);
    }
    pthread_mutex_unlock(&lock);
 }