Fill each cell with a single digit and draw a “train” that covers every cell in the grid. The train consists of 4 carriages of equal length and each carriage is formed of an orthogonal path of cells. A carriage doesn't touch itself, not even diagonally. Adjacent digits along a carriage are consecutive. An X connects the end cells of two carriages, which sum to 10. The black fly connects two digits with a 1:2 ratio. Identical digits may not touch each other orthogonally. A digit on the train indicates how many times that digit appears on the train.