def HanoiTowers(start, via, target, n):
    """ computes a list of discs steps to move a stack of n discs from
    rod "start" to rod "target" employing intermediate rod "via" """
    if n>0:
        HanoiTowers(start, target, via, n-1)
        print("disk", n, "from", start, "to", target)
        HanoiTowers(via, start, target, n-1)
      

HanoiTowers("A", "B", "C", 3)



def hanoi_move(start, via, target, n, k):
    """ finds the k-th move in an Hanoi Towers instance
    with n discs """
    if n<=0:
        print ("zero or fewer disks")
    elif k<=0 or k>=2**n or type(k)!=int:
        print("number of moves is illegal")
    elif k==2**(n-1):
        print("disk", n, "from", start, "to", target)
    elif k < 2**(n-1):
        hanoi_move(start, target, via, n-1, k)
    else:
        hanoi_move(via, start, target, n-1, k-2**(n-1))