var
  i,n,l,j:longword; found:boolean;
begin
  readln(n);
  repeat
  found:=False;
  for j:=3 to n div 2 do
  begin
    if n mod j=0 then
    begin
      found:=True;
      break;
    end;
  end;
  if found then n:=j;
  until not found;
  writeln(n-1);
  readln;
end.

Please help me to optimize my code. It's 0.405 sec

 for j := 3 to sqrt(n) do  will help you :)

> for j := 3 to sqrt(n) do  will help you :)

will it? for sqrt(8) = 2.8, but answer should be 4 - 1 = 3