Hello friends I'm working on a mini project (8-puzzle) for which I need the distance manhattan and have programmed it in the following way

valabs[a_, b_] := If [a > b, a - b, b - a]
manhattan[tablero_List] := Module[{i, j, x, y, cuenta = 0},
  For[i = 1, i <= 3, i++,
   For[j = 1, j <= 3, j++,
     If[tablero[[i, j]] == 0
       ,
       cuenta += 0;
       ,
       x = Quotient[tablero[[i, j]] - 1, 3] + 1;
       y = Mod[tablero[[i, j]] - 1, 3] + 1;
       cuenta = cuenta + valabs[x, i] + valabs[y, j];
       ];
     ];
   ];
  cuenta
  ]

Remember that you should not count zero, wanting to do the same with function ManhattanDistance get a different value, here is an example. With my function

In[1]:= manhattan[{{2, 1, 5}, {6, 3, 4}, {8, 0, 7}}]

Out[1]= 13

Now with ManhattanDistance

In[2]:= ManhattanDistance[{{2, 1, 5}, {6, 3, 4}, {8, 0, 7}}, {{1, 2,    3}, {4, 5, 6}, {7, 8, 0}}]

Out[2]= 11  

Someone could say why am I having such a result, I think that there is some trick to be able to do the same, it would be of much help some guidance, because I plan to keep using ManhattanDistance later in my code, greetings to all.