One who ate, and forgot and did not recite Bircas HaMazon, Beis Shammai say: He should return to his place and recite Bircas HaMazon. But Beis Hillel say: He may recite Bircas HaMazon in the place where he remembered. Until when can he recite Bircas HaMazon? Until the food in his stomach has been digested.