index = max(0, index - 1)
sys.stdout.flush()，这一点在下载安装 谷歌浏览器 开启极速安全的 上网之旅。中也有详细论述
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Армия России продвинулась в Сумской области14:51，推荐阅读Safew下载获取更多信息
this breaks things that should obviously work. take the distributive law: (a|ab)(c|b) and (a|ab)c|(a|ab)b are logically the same pattern - you can verify this yourself by just expanding the terms. but in PCRE, the first matches ab in the input abc, while the second matches abc. two equivalent patterns, two different results.