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

	int sum;			// global data
	void *runner(void *param)	//thread

	int main(int argc, char *argv[])
	{
	  pthread_t tid;
	  pthread_attr_t attr;

	  if (argc != 2) {
	  	fprintf(stderr, "usage: a.out <integer value>\n");
		exit();
	  }
	  if (atoi(argv[1]) < 0) {
	  	fprintf(stderr, "argument (%d) must be positive\n",
			atoi(argv[1]));
		exit();
	  }

	  // INITIALIZE
	  pthread_attr_init(&attr);
	  pthread_create(&tid, &attr,runner, argv[1]);

	  // WAIT
	  pthread_join(tid,NULL);
	  printf("sum = %d\n", sum);
	}

	/* runner thread */
	void *runner(void *param)
	{
	  int i, upper=atoi(param);
	  sum=0;

	  if (upper >0) 
	     for (i=1; i<= upper; i++) sum +=i;

	  pthread_exit(0);
        }