rand() stops working when I try to do stuff with it [duplicate]

I'm trying to understand how the rand() function works. I started out with a simple for loop printing random numbers each time, and that seems to work perfectly, but as soon as I add more code (in this case I'm trying to clamp the random number between 1 and 20, and doing some other stuff to get the probabiliy of two events happening) it stops working and only returns 0s.

Any idea what's happening?

int getRando(int bNumber)
{
    int i, r;
    
    while(r>32760)
    {
        r = rand();
    }
    
    for(i=1;i<=bNumber;i++)
    {
       if (r <= (1638 * i))
       {
            r = i;
            break;
       } 
    }
    
    return r;
}




int main(int argc, char *argv[]) {
    srand(time(NULL));   
    
    int i, r, primaBianca = 0, primaNera = 0;
    
    for(i=0;i<1000;i++)  //this works
    {
        r = rand();
        printf ("%d\n",r);
    }
    
    
    for (i=0; i<1000;i++) 
    {
        r = getRando(20);   //from this point on it only returns zeroes
        
        if  (r<=12)
        {
            r = getRando(20);
            if (r<=12) primaBianca++;
        }
        else  
        {
            r = getRando(19);
            if (r<=12) primaNera++; 
        }
    }
    
    printf ("prima pallina bianca: %d\n",primaBianca);
    printf ("prima pallina nera: %d\n",primaNera);
    return 0;
    
}