Hexa Kropki (440)

Fill in the whole figure with digits 1 to N (N is the maximum size of a row) so that each row (in any of the three directions) contains each digit at most once. If there is a white dot between a pair of orthogonally adjacent cells, then the cells must contain numbers whose difference is exactly one. If there is a black dot between a pair of orthogonally adjacent cells, then the cells must contain numbers whose quotient is exactly two. There can be either black or white dot between 1 and 2. All possible dots have been given.

Reference: WPC 2016 (65)