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

#define DEBUG 1
#define ITERATIONS 100000

sem_t high_sem, low_sem;
int counter = 0;

void* high() {
    while (counter < ITERATIONS) {
        sem_wait(&high_sem);
        #if DEBUG
        printf("%d: HIGH\n", counter);
        #endif
        sem_post(&low_sem);
        counter++;
    }
    return NULL;
}

void* low() {
    while (counter < ITERATIONS) {
        sem_wait(&low_sem);
        #if DEBUG
        printf("%d: LOW\n", counter);
        #endif
        sem_post(&high_sem);
        counter++;
    }
    return NULL;
}

int main() {
    pthread_t high_thread, low_thread;

    sem_init(&high_sem, 0, 1); // high_sem starts 
    sem_init(&low_sem, 0, 0);

    pthread_create(&high_thread, NULL, high, NULL);
    pthread_create(&low_thread, NULL, low, NULL);

    pthread_join(high_thread, NULL);
    pthread_join(low_thread, NULL);

    sem_destroy(&high_sem);
    sem_destroy(&low_sem);

    return 0;
}