Semaphores not working properly in terminal

Question

I am trying to use semaphores but they are not working in the terminal for some reason.

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

sem_t mySem;


void *p1a(void *arg) 
{
    sem_wait(&mySem);
    printf("B");
    return NULL;
}
void *p2a(void *arg){
    
    printf("A");
    sem_post(&mySem);
    return NULL;
}


int main(void) 
{
    sem_init(&mySem, 0, 0);
    pthread_t p1;
    pthread_t p2;
 
    
    
    if (pthread_create(&p1, NULL, p1a, NULL))
    {
        printf("Error creating thread.\n");
        exit(1);
    }
    sleep(2);
    if (pthread_create(&p2, NULL, p2a, NULL))
    {
        printf("Error creating thread.\n");
        exit(1);
    }



  
    pthread_join(p1,NULL);
    pthread_join(p2,NULL);

    sem_destroy(&mySem);
    exit(0);
}

The result I get is BA but when I ran the same code in replit, it printed AB. Im not sure why this is happening and any help would be appreciated.