plsql code to find maximum of 3 numbers

Declare

          a number;

          b number;

          c number;

          d number;

Begin

          dbms_output.put_line('Enter a:');

          a:=&a;

          dbms_output.put_line('Enter b:');

          b:=&b;

          dbms_output.put_line('Enter c:');

          c:=&b;

          if (a>b) and (a>c) then

                    dbms_output.putline('A is Maximum');

          elsif (b>a) and (b>c) then

                    dbms_output.putline('B is Maximum');

          else

                    dbms_output.putline('C is Maximum');

          end if;

End;