A moving picture decoding apparatus, method, and medium for decoding a current block are provided. A first candidate is derived from a first motion vector that has been used to decode a first block. The first block is adjacent to the current block. A second candidate having a second motion vector that includes a non-zero value is derived. The non-zero value is assigned to a corresponding reference picture. The second motion vector is not derived by decoding a block adjacent to the current block. A candidate is selected from a plurality of candidates, including the first candidate and the second candidate. The current block is decoded using the selected candidate. The second candidate includes the non-zero value of the corresponding reference picture, selected from a plurality of referable reference pictures.