为什么WA了，急

const
 fx:array[1..8]of longint=(1,2,-1,-2,1,2,-1,-2);
 fy:array[1..8]of longint=(2,1,2,1,-2,-1,-2,-1);
var
 map:array[1..400,1..400]of longint;
 father,x,y:array[1..1000]of longint;
 i,j,n,m,sx,sy:longint;
 function check(a,b:longint):boolean;
 begin
  if (a>=1)and(a<=n)and(b>=1)and(b<=m)and(map[a,b]=-1) then exit(true);
  exit(false);
 end;
 procedure bfs;
  var i,head,tail,xx,yy:longint;
 begin
  x[1]:=sx; y[1]:=sy;
  head:=0; tail:=1;
  map[sx,sy]:=0;
  repeat
   inc(head);
   for i:=1 to 8 do
    if check(x[head]+fx[i],y[head]+fy[i]) then
     begin
      xx:=x[head]+fx[i]; yy:=y[head]+fy[i];
      father[head]:=tail;
      inc(tail);
      x[tail]:=xx; y[tail]:=yy;
      map[xx,yy]:=map[x[head],y[head]]+1;
     end;
  until(head=tail);
 end;
begin
 read(n,m,sx,sy);
 for i:=1to n do
  for j:=1 to m do
   map[i,j]:=-1;
 bfs;
 map[sx,sy]:=0;
 for i:=1 to n do
 begin
  for j:=1 to m do
    write(map[i,j],'     ');
  writeln;
 end;
end.