program faro_shuffle;
    loop for test in [8, 24, 52, 100, 1020, 1024, 10000] do
        print(lpad(str test, 5) + " cards: " + lpad(str cycle [1..test], 4));
    end loop;

    op cycle(l);
        start := l;
        loop until l = start do
            l := shuffle l;
            n +:= 1;
        end loop;
        return n;
    end op;

    op shuffle(l);
        return [l(mapindex(i,#l)) : i in [1..#l]];
    end op;

    proc mapindex(i, size);
        return if odd i then i div 2+1 else (i+size) div 2 end;
    end proc;
end program;