求X和Y两个字符串的最长公共子序列。（X和Y字符串分别存放在ASCII码文件2X.txt和2Y.txt中)

要求：根据动态规划法基本设计思想，将实现任务的C语言程序代码和运行结果填写在试卷上。

-Two strings X and Y find the longest common subsequence. (X and Y strings are stored in ASCII files 2X.txt and 2Y.txt in) requirements: According to the basic design of dynamic programming ideas to achieve the mission of the C language code and fill in the papers on the results.