“火烧连营”是三国演义中的著名典故之一广为流传，假定文本文件c1.txt是火烧连营中的军营分布图，每个字符A代表一个营帐，营帐是可燃物，其他字符代表不可燃的空白地段，文件共有40行70列，请你编写程序，读入该文件的内容，再从键盘输入任意点的x和y值（x<70,y<40）作为着火点，“火烧连营”后，被燃烧的营帐标上字符’X’，并把整个结果输出到文件c2.txt中。- Baked wheaten cake joins camp　is one of the famous allusions widely circulated in the romance of The Three Kingdoms, assume that A text file c1. TXT is A barracks in wheaten cake joins camp fire distribution, each character represents A camp, A camp is fuel, and other characters on behalf of incombustible blank area, file A total of 40 line 70 columns, please write A program that reads the contents of the file, then x and y values of an arbitrary point input　the keyboard (x < 70, y < 40) as A fire,　baked wheaten cake joins camp , after the camp is burned in characters　x　, the whole results output to A file and c2. TXT.