输入一个句子（由空格分隔的若干个词）将该句子按如下的要求输出：

1.第偶数个词反序，第奇数个词不反序

2.个词之间只留一个空格

3.句首和句尾不留空格-importation of a sentence (space separated by the number of words) Revise the sentence requested by the following output : 1. even the first-term anti-sequence, section 000 odd word does not fight sequence two. between the words out, leaving only a blank 3. the first sentence and the end of the sentence without leaving spaces