SQL to fetch first day and last day of the month

SELECT LEVEL,
       TO_CHAR (TRUNC (ADD_MONTHS (SYSDATE, LEVEL - 1), 'MM'), 'DD-MON-RRRR'),
       TO_CHAR (LAST_DAY (ADD_MONTHS (SYSDATE, LEVEL - 1)), 'DD-MON-RRRR')
FROM DUAL
CONNECT BY LEVEL <= 100;