program milkweed;
var
  map:array[0..101,0..101]of longint;
  ma:array[0..101,0..101] of boolean;
  i,j,n,m,a,b,t,X:longint;
  s:string;
procedure sss;
var
  i,j:longint;
begin
  X:=0;
  for i:=1 to m do begin
    for j:=1 to n do begin
      if (ma[i,j])and(map[i,j]<>-1) then begin
        INC(X);
        if map[i+1,j]=0 then begin
           ma[i+1,j]:=true;
           map[i+1,j]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

        if map[i-1,j]=0 then begin
           ma[i-1,j]:=true;
           map[i-1,j]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i+1,j+1]=0 then begin
           ma[i+1,j+1]:=true;
           map[i+1,j+1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i+1,j-1]=0 then begin
           ma[i+1,j-1]:=true;
           map[i+1,j-1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i,j+1]=0 then begin
           ma[i,j+1]:=true;
           map[i,j+1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i,j-1]=0 then begin
           ma[i,j-1]:=true;
           map[i,j-1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i-1,j+1]=0 then begin
           ma[i-1,j+1]:=true;
           map[i-1,j+1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;

         if map[i-1,j-1]=0 then begin
           ma[i-1,j+1]:=true;
           map[i-1,j+1]:=map[i,j]+1;
           if t<map[i,j] then t:=map[i,j]+1;
         end;
         ma[i,j]:=false;
      END;
   END;
 end;
end;
begin
  assign(input,'milkweed.in');
  assign(output,'milkweed.out');
  reset(input); rewrite(output);
  readln(n,m,a,b);
  t:=0;
  for i:=0 to 101 do begin
    for j:=0 to 101 do begin
      map[i,j]:=-1;
      ma[i,j]:=false;
    end;
  end;
  for i:=1 to m do begin
    readln(s);
    for j:=1 to n do if s[j]='.' then map[i,j]:=0 ;
  end;
  map[m-b+1,a]:=1;  ma[m-b+1,a]:=true;
  for i:=1 to n*m do begin
    SSS;
    if x=0 then break;
  end;
  for i:=1 to n do begin
    for j:=1 to m do begin
      if map[j,i]=0 then begin
        writeln(-1);
        halt;
        close(input); close(output);
      end;
    end;
  end;
  writeln(t);
  close(input); close(output);

end.