I get wrong answer at test 3?
why?
this is my program:
program gh;
const
 x:array[1..4] of integer=(-1,0,1,0);
 y:array[1..4] of integer=(0,-1,0,1);
var
 a,d,f,g,h,j,k,i,l,m,n:longint;
 s,z,c:string;
 procedure work(q:integer);
 var
  i,j,k,l:longint;
  v:string;
 begin
  if q=17 then
   begin
    if (pos('w',s)=0) and (g<m) then
     m:=g;
   end
  else
   begin
    v:=s;
    i:=((q-1) div 4)+1;
    j:=q-(i-1)*4;
    if s[q]='w' then
     s[q]:='b'
    else
     s[q]:='w';
    for l:=1 to 4 do
     if (i+y[l]>0) and (i+y[l]<5) and  (j+x[l]<5) and (j+x[l]>0) then
      if s[(i+y[l]-1)*4+j+x[l]]='w' then
       s[(i+y[l]-1)*4+j+x[l]]:='b'
      else
       s[(i+y[l]-1)*4+j+x[l]]:='w';
    g:=g+1;
    work(q+1);
    g:=g-1;
    s:=v;
    work(q+1);
   end;
 end;
begin
 s:='';
 for i:=1 to 4 do
  begin
   readln(z);
   s:=s+z;
  end;
 g:=0;
 m:=1000000;
 work(1);
 if m=1000000 then
  writeln('Impossible')
 else
  writeln(m);
end.

Edited by author 06.09.2006 18:24

Try this!
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Your answer is 4, but the right answer is 0

Thank you vary much!
I get ac.
But how can you get the testdata?
Can you give me some ural's testdata?
This is my e-mail:    liuxuelxg@163.com
Thank you!

I haven't got the testdata!)) That was just the first test I tried to check your program!))