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

sem_t S1,S2;

void* P1()
{
	 
        sem_wait(&S1);
	printf(" A ");
	sem_post(&S2);
      pthread_exit(0); /* exit */
}

void* P2()
{
	 
	printf(" B ");
	sem_post(&S1);
      pthread_exit(0); /* exit */
}

void* P3()
{
         
	sem_wait(&S2);
	printf(" C ");
      pthread_exit(0); /* exit */

}



int main()
{
	sem_init(&S1, 0, 0);
	sem_init(&S2, 0, 0);
	pthread_t t1,t2,t3;

	pthread_create(&t1,NULL,P1,NULL);
 
	pthread_create(&t2,NULL,P2,NULL);
	
	pthread_create(&t3,NULL,P3,NULL);
	
    pthread_join(t1,NULL);
	pthread_join(t2,NULL);
	pthread_join(t3,NULL);
	printf(" \n ");
	return 0;
}