1. A method of deriving a motion vector of a bi-predictive block based on a list 1 motion vector of a co-located block in a reference picture using a bit operation, comprising: selecting a list 1 motion vector of the co-located block in a first list 1 reference picture as the motion vector for deriving list 0 and list 1 motion vectors of the bi-predictive block, if the co-located block only has the list 1 motion vector, the first list 1 reference picture being a type of reference picture permitted to be located temporally before or after a current picture, the selected list 1 motion vector pointing a second list 1 reference picture which is a reference picture of the first list 1 reference picture, and the current picture including the bi-predictive block; and deriving at least one motion vector of the bi-predictive block by applying a bit operation to the selected motion vector.