Anonymous

bool key_check (int *ls) {
    int v = 3,
	i = 0;
    while (i < 12) {
	v += (ls [i++] ^ (v * 2));
    }
    return ls [12] == v % 10;
}

    
main () {
    int key [] = {3, 1, 1, 3, 3, 0, 0, 2, 4, 0, 3, 9, 6};

    printf ("%d\n", key_check (key));
}