Thank you Tran Nam Trung for your help on problem 1183. But I didn't
understand your idea. Can you explain it more clearly(espesially
about [i,j] - what i,j mean?)

>  Thank you Tran Nam Trung for your help on problem 1183. But I
didn't
> understand your idea. Can you explain it more clearly(espesially
> about [i,j] - what i,j mean?)
Very happy to help you. D[i,j] means the minnimum number of
characters needed to change the sequence from i to j become correct
sequence. So the answer to the prob is D[1,length(s)].
If you still don't understand me, email me at : trungduck@yahoo.com

Program t1183;

Const MaxN = 100;

Var   D        : array[1..MaxN,1..MaxN]of byte;
      i,j,k,q  : integer;
      len      : integer;
      min      : integer;
      S        : String;

Function GetAns(l1,l2 : byte) : String;
Var j : integer;
 begin
  if l1=l2 then begin
    if (s[l1]='(')or(s[l2]=')') then begin
      GetAns:='()';
      exit;
     end;
    if (s[l1]='[')or(s[l2]=']') then begin
      GetAns:='[]';
      exit;
     end;
   end;
  if ((s[l1]='(')and(s[l2]=')'))or
     ((s[l1]='[')and(s[l2]=']')) then begin
       if l1+1<=l2-1 then
        if D[l1,l2]=D[l1+1,l2-1] then begin
         GetAns:=s[l1]+GetAns(l1+1,l2-1)+s[l2];
         exit;
        end;
       if l1+1>l2-1 then begin
         GetAns:=s[l1]+s[l2];
        end;
     end;
  for j:=l1 to l2-1 do
   if D[l1,j]+D[j+1,l2]=D[l1,l2] then begin
    GetAns:=GetAns(l1,j)+GetAns(j+1,l2);
    exit;
   end;
 end;

begin
 Readln(S);
 len:=length(S);
 if len=0 then begin
  Writeln('');
  Halt;
 end;
 fillchar(D,SizeOf(D),255);
 for i:=1 to len do D[i,i]:=1;
 for k:=1 to len-1 do
  for i:=1 to len-k do
   for j:=i+k to len do begin
   if ((s[i]='(')and(s[j]=')'))or
      ((s[i]='[')and(s[j]=']')) then
       if i+1<=j-1 then D[i,j]:=D[i+1,j-1] else D[i,j]:=0;
   for q:=i to j-1 do
    if D[i,q]+D[q+1,j]<D[i,j] then
     D[i,j]:=D[i,q]+D[q+1,j];
  end;
 Writeln(GetAns(1,len));
end.

I don't know why. You can try with this test : Input : 100
chacacters "(".

> I don't know why. You can try with this test : Input : 100
> chacacters "(".