program p2;

{$APPTYPE CONSOLE}

const
  n =  15 ;
  m =  25 ;

var
  a: array[ 1 ..n] of LongWord = ( 5 ,  6 ,  7 ,  8 ,  9 ,  17 ,  2 ,  3 ,  4 ,  11 ,  7 ,  13 ,  25 ,  20 ,
     24 );

procedure FindDupe;
var
  p: LongWord; //address of bitmap
  s: LongWord; //size of bitmap
  i: LongWord;
begin
  s := m div  8 ;
  if m mod  8  <>  0  then
    Inc(s);
  p := LongWord(GetMemory(s));
  for i :=  1  to n do
    begin
      if (PByte(p + (a[i] div  8 ))^ shr (a[i] mod  8 )) and  1  =  0  then // if bit number a[i] is not set then ...
        Inc(PByte(p + (a[i] div  8 ))^, ( 1  shl (a[i] mod  8 ))) // ... set the bit.
      else // the bit number a[i] has already been set.
        begin
          Writeln('Duplicate element is: ',a[i]);
          Break;
        end;
    end;
  FreeMemory(Pointer(p));
end;

begin
  FindDupe;
  Readln;
end.