前缀码：任何一个字符的编码都不是同一字符集中另一个字符的编码的前缀。



请编写一个程序，判断输入的n个由1和0组成的编码是否为前缀码。如果这n个编码是前缀码，则输出 YES”；否则输出第一个与前面编码发生矛盾的编码。-Prefix: Any character encoding is not the same character set encoding another character prefix. Write a program, n one by the ones and zeros of the input code judging whether the prefix. If n is coded prefix, the output " YES"　 otherwise, outputs a contradiction with previous encoding encoding.