Why WA 8? Please help me ! I tested my programm many times, but did'not find a mistake. Maybe someone tell me where is wrong or give me same test.
Sorry for my bad english.

Here is my code:
program Project2;

{$APPTYPE CONSOLE}
uses windows;
type din=array of longint;
type IntMas=array[1..2000] of longint;
var mas,mas2:din;
    pre,rez:intMas;
    n,i,dlin,dlin2,kol,u,y,save,KOLM,a,b,sr,MAX,num,del,l,r:longint;
    f:text;
   // lMas:array[1..2000,1..2000] of longint;
   DELTA:array[0..1000000000] of boolean;
    T:BOOLEAN;
    t1,t2,t3,t4:_SYSTEMTIME;



procedure sort(var d,d2:din;var l:longint);
var dlin,dlin2:longint;
     mas2,mas3,Dmas2,Dmas3:din;
begin
t:=false;


dlin:=l div 2;
dlin2:=l-dlin;
setlength(mas2,dlin+1);
setlength(Dmas2,dlin+1);
for i:=1 to dlin do
  mas2[i]:=d[i];
for i:=1 to dlin do
  Dmas2[i]:=d2[i];

setlength(mas3,dlin2+1);
setlength(Dmas3,dlin2+1);
for i:=1 to dlin2 do
  mas3[i]:=d[i+dlin];
for i:=1 to dlin2 do
  Dmas3[i]:=d2[i+dlin];

if dlin>1 then
  begin
  sort(mas2,Dmas2,dlin);
  end;

if dlin2>1 then
  begin
  sort(mas3,Dmas3,dlin2);
  end;
kol:=0;
i:=1;
u:=1;
L:=dlin+dlin2;
while kol<l do
  begin

  if mas2[i]<mas3[u] then
    begin
    inc(kol);
    d[kol]:=mas2[i];
    d2[kol]:=Dmas2[i];
    if i+1<=dlin then
      inc(i)
    else
      begin
      for y:=u to dlin2 do
        begin
        d[kol+y-u+1]:=mas3[y];
        d2[kol+y-u+1]:=Dmas3[y];

        end;
      break;
      end;
    end
  else
    begin
    inc(kol);
    d[kol]:=mas3[u];
    d2[kol]:=Dmas3[u];
    if u+1<=dlin2 then
      inc(u)
    else
      begin
      for y:=i to dlin do
        begin
        d[kol+y-i+1]:=mas2[y];
        d2[kol+y-i+1]:=Dmas2[y];
        end;
      break;
      end;
    end
  end;

//sort()
end;

begin
{assign(f,'input.txt');
reset(f);}
readln({f,}n);



setlength(mas,n+1);
setlength(mas2,n+1);
for i:=1 to n do
  begin
  read({f,}mas[i]);
  mas2[i]:=i;
  end;

t:=false;
if n>1 then
sort(mas,mas2,n);

rez[1]:=1;
kolM:=1;
DELTA[0]:=true;

for i:=1 to n do
  for u:=i+1 to n do
    if not DELTA[mas[u]-mas[i]] then
      begin
      del:=mas[u]-mas[i];
      DELTA[del]:=true;
      num:=mas[u];
      num:=num+del;

      kol:=2;
      pre[1]:=mas2[u];
      pre[2]:=mas2[i];
      l:=u;
      r:=n;
      while true do
        begin
        if mas[l]=num then
          begin

          inc(kol);
          pre[kol]:=mas2[l];
          num:=num+del;
          l:=l;
          r:=n;
       //   break;
          end;

        if mas[r]=num then
          begin

          inc(kol);
          pre[kol]:=mas2[r];
          num:=num+del;
          l:=r;
          r:=n;
         // break;
          end;
        if (mas[r]<>num) and(mas[l]<>num) then
          begin
          if ((abs(r-l)=1) or (abs(r-l)=0))   then
            begin
            if kol>kolM then
              begin
              for l:=1 to kol do
                rez[l]:=pre[l];
              kolm:=kol;
              end;
            break;
            end;
          if mas[(l+r)div 2]<num then
            l:=(l+r)div 2
          else
            r:=(l+r)div 2;
          end;



        end;

      end;


writeln(kolM);
for i:=1 to kolM do
  begin
  write(rez[i]);
  write(' ');

  end;
  //readln;

end.

9
1 3 5 11 2 3 4 7 9
answer:
6
1 2 3 8 9 4