Something

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

/* cheap PRNG */

int main()
{
        char *s;
        setbuf(stdout, NULL);
        if(fork())
                s="B\n";
        else
                s="A\n";
        for(; *s != '\0'; s++)
                putc(*s, stdout);
        exit(0);
}