规则Rules：
标准数独基础上，每个虚线框内数字不重复，角标是框内数字之和。本题中，角标里的数字使用了未知数进行表示，相同的字母代表相同的数字，不同的字母也有可能代表相同的数字。
Classic rules applied. Additionally, numbers cannot repeat in each cage, clue is the sum of the numbers. Specially in this puzzle, clues are instead by unknown number X and Y. Same letter means same numbers, different letters may mean same or different numbers.
