text: declare 
      a number(2);
      b number(2);
      s number(2);
    function sum2no (a in number,b in number)return number is
      begin
        s:=a+b;
        return s;
      end;
  begin
   a:=:a;
   b:=:b;
   s:=sum2no(a,b);
   dbms_output.put_line('sum of '|| a||' and '||b||' is :-'||s);
  end;