import copy

boardsize=6
_kmoves = ((2,1), (1,2), (-1,2), (-2,1), (-2,-1), (-1,-2), (1,-2), (2,-1)) 


def chess2index(chess, boardsize=boardsize):
    'Convert Algebraic chess notation to internal index format'
    chess = chess.strip().lower()
    x = ord(chess[0]) - ord('a')
    y = boardsize - int(chess[1:])
    return (x, y)

def boardstring(board, boardsize=boardsize):
    r = range(boardsize)
    lines = ''
    for y in r:
        lines += '\n' + ','.join('%2i'% board[(x,y)] if board[(x,y)] else '  '
                                 for x in r)
    return lines

def knightmoves(board, P, boardsize=boardsize):
    Px, Py = P
    kmoves = set((Px+x, Py+y) for x,y in _kmoves)
    kmoves = set( (x,y)
                  for x,y in kmoves
                  if 0 <= x < boardsize
                     and 0 <= y < boardsize
                     and not board[(x,y)] )
    return kmoves

def accessibility(board, P, boardsize=boardsize):
    access = []
    brd = copy.deepcopy(board)
    for pos in knightmoves(board, P, boardsize=boardsize):
        brd[pos] = -1
        access.append( (len(knightmoves(brd, pos, boardsize=boardsize)), pos) )
        brd[pos] = 0
    return access

def knights_tour(start, boardsize=boardsize, _debug=False):
    board = {(x,y):0 for x in range(boardsize) for y in range(boardsize)}
    move = 1
    P = chess2index(start, boardsize)
    board[P] = move
    move += 1
    if _debug:
        print(boardstring(board, boardsize=boardsize))
    while move <= len(board):
        P = min(accessibility(board, P, boardsize))[1]
        board[P] = move
        move += 1
        if _debug:
            print(boardstring(board, boardsize=boardsize))
            input('\n%2i next: '% move)
    return board

if __name__ == '__main__':
    while 1:
        boardsize = int(input('\nboardsize: '))
        if boardsize < 5:
            continue
        start = input('Start position: ')
        board = knights_tour(start, boardsize)
        print(boardstring(board, boardsize=boardsize))