#define MAX 13

void shuffle() {
    int hold;

    for(i = 0; i < MAX; i++) {
        filenames[i] = i;
    }

    for(i = 0; i < MAX; i++) {
        r = rand(MAX);
        hold = filenames[i];
        filenames[i] = filenames[r];
        filenames[r] = filenames[i];
    }
}