R’ Eliezer says: A man is obligated to eat fourteen meals in the succah, one each day and one each night. But the Sages say: This matter has no fixed obligation, except for the night of the first Yom Tov of the Festival only.  R’ Eliezer further stated: Whoever did not eat [in the succah] on the night of the first Yom Tov, must compensate for it on the night of the last Yom Tov. But the Sages say: This matter has no compensation. About this matter it is said: A twisted thing cannot be made straight, and what is not there cannot be numbered.

A person who had his head and most of his body inside the succah and his table inside the house —- Beis Shammai invalidate [the succah] and Beis Hillel validate it.  Said Beis Hillel to Beis Shammai, “Did it not happen that the elders of Beis Shammai and the elders of Beis Hillel went to visit R’ Yochanan son of the Choranite and found him sitting with his head and most of his body inside the succah and his table within the house, and they said nothing to him?”  Beis Shammai replied to them, “Is that [your] proof? Actually, they said to him, `If this is how you have [always] conducted yourself, [then] you have never in your life fulfilled the mitzvah of succah.’ ”