#include<stdlib.h>
#include<stdio.h>
#include<pthread.h>

int global_variable;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

void * change_value(void * arg)
{
  int operation = (int) arg, i;
  for (i = 0; i < 100000; i++)
    {
      pthread_mutex_lock(&mutex);
      if (operation == 0)
      {
        global_variable++;
      }
      else
      {
        global_variable--;
      }
      pthread_mutex_unlock(&mutex);
      printf("%d ", global_variable);
      fflush(stdout);
    }
}

int main()
{
  printf("Hello \n");
  pthread_t addition, substraction;
  pthread_create(&addition, NULL, change_value, (void *) 0);
  pthread_create(&substraction, NULL, change_value, (void*) 1);
  pthread_join(addition, NULL);
  pthread_join(substraction, NULL);
  pthread_exit(NULL);

  return 0;
}