编写一个截取字符串的控制台操作，输入为一个字符串和字节数，输出为按字节截取的字符串。 但是要保证汉字不被截半个，如"我ABC",4，应该截为"我AB"，输入"我ABC汉DEF"，6，应该输出为"我ABC"而不是"我ABC+汉的半 个"。-Write a string interception console operation, the input is a string and the number of bytes, output intercepted by byte string. But to ensure that the kanji is not truncated half, such as " I ABC" , 4, should be cut for " AB" , input " I ABC Han DEF, 6, should be output for"　ABC " instead of"　I ABC+ Han half. "