The Lost Number is an optional boss in Final Fantasy VII. After entering the right combination for the safe in the Shinra Mansion, it will attack the player party. The combination is: (Right 36), (Left 10), (Right 59), (Right 97). After its defeat, the player obtains Cosmo Memory, the Odin Materia and a key to the Mansion's basement, which can be used to recruit Vincent to the party.