#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
 
sem_t mutex;
int shared = 0;
 
void* critical_section(void* arg)
{
    sem_wait(&mutex);
    int temp = shared;
    temp++;
    sleep(1);
    shared = temp;
    printf("Thread %ld: shared = %d\n", (long)arg, shared);
    sem_post(&mutex);
    return NULL;
}
 
int main()
{
    pthread_t t1, t2;
    sem_init(&mutex, 0, 1);
 
    pthread_create(&t1, NULL, critical_section, (void*)1);
    pthread_create(&t2, NULL, critical_section, (void*)2);
 
    pthread_join(t1, NULL);
    pthread_join(t2, NULL);
 
    sem_destroy(&mutex);
    return 0;
}

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