Rainbow Sudoku is a ring of four individual 9X9 Rainbow Sudokus (九九彩虹數獨), arranged in a very compact 15X15 manner. The Rainbow Sudoku is a traditional Sudoku painted with nine different colors , and with an additional restriction. If we exam all the nine 3X3 square blocks, the numbers at the same colored squares, or on the same positions, of all the 3X3 square blocks should also not be repeated (每個3X3小九宮上相同位置,或同颜色,方塊中的數字也不能重複).