字符串不行？为什么0分？

···

var
  s:string[15];  i:longint;
begin
  readln(s);
  if s[1]='-' then 
   begin
    write('-');
    delete(s,1,1);
   end;
  if s[length(s)]<>'0' then write(s[length(s)]);
  for i:=length(s)-1 to 1 do write(s[i]);
end.  
···