1. Consider the points A(2, 1, 1), B(3, 0, 2), C(4, 2, 1) and D(3, m, 0). If the volume of the parallelepiped determined by the vectors \overrightarrow{AB}, \overrightarrow{AC}, and \overrightarrow{AD} is 4, then the sum of all possible values of m is