Place the digits 1-9, once each, in every row, column and marked region. When digit z is in cell (x, y) then digit y is in cell (x, z) and digit x is in cell (z, y).
Place the digits 1-9, once each, in every row, column and marked region. When digit z is in cell (x, y) then digit y is in cell (x, z) and digit x is in cell (z, y).