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As Numberland's best detective, you thought you'd seen it all.
身为数字王国的最强侦探，你觉得什么大风大浪都见过了。
But the desiccated corpses of prominent natural numbers -- whole numbers greater than 0 -- have been showing up all over the city for the past week.
然而知名自然数的干尸--自然数是比0大的整数--在过去几周内遍布整座城市。
All of Digitopolis is on lockdown from sundown to sunrise, and it's still not enough to stop what can only be described as a vampiric feeding frenzy.
整座数字城邦在日落到日出间实施宵禁，但仍不足以阻止吸血鬼的凶暴攻击。
The police are helpless, and have turned to you. You put the missing persons case you've been investigating on hold and study the evidence.
警方备感无助，于是找上了你。你暂时放下手边的人口失踪案件，先研究证据。
Here's what you know: most victims have been completely drained of their life's essence.
这些是你所知道的：多数被害人的身体被吸干。
Some have a thin line of slime separating digits -- some of which were drained and others spared.
有些被一条条黏液切出不同的位数，有些位数被吸干，其他则没有。
Which leads you to mystery one: what's the significance of the slime-lines, and why are certain digits untouched?
这让你必须面对谜题一：黏液线段有什么重要性，而且为何特定位数毫发无伤？
Let's start by looking for a pattern in the victims. Why have some been fully drained, and some slimed?
我们先从观察被害人的模式开始。为何有人被完全吸干，有人则有黏液？
Well, the slime-lined are in their prime -- which is to say they're prime numbers, divisible only by 1 and themselves.
黏液线段出现在质数--只能被1和自己整除的数。
Not a single one of the unslimed numbers, on the other hand, is.
另一方面，没有一个未被黏液切开的数是质数。
Furthermore, the drained parts of the slimed primes are not, themselves, prime. When 71 got slimed, 7 was prime, but 1 was not.
而且，带有黏液的质数中，被吸干的部分也并非质数。71有黏液，7是质数，但1不是。
If 461 had been split into 4 and 61, the right side would have been prime, but instead it was split further into non-prime digits.
如果461被切成4和61，61就会是质数，但他被进一步切成不是质数的数。
And when 2099 got slimed, the attacker went with 20 and 99, and was able to drain both. So you have a big problem.
2099有黏液，攻击者切成20和99，如此便能两者都吸干。于是你遇到一个大问题。
There are infinite potential victims: all non-prime numbers, and all prime numbers that can be slime-lined to reveal at least one non-prime number.
有无数个可能的被害人：所有不是质数的整数、所有可被黏液切割出至少一个非质数的质数。
In fact, you can only think of a few numbers that aren't vulnerable. First of all, the one digit primes: 2, 3, 5, and 7.
事实上，你只想得到少数几个数不会被害。首先是一位数的质数：2、3、5、7。
Then primes like 23, which could only be split into 2 and 3, both prime. These numbers are familiar, but why?
然后是像23的质数，只能切成2和3，都是质数。这些数很眼熟，为什么？
Aha! Your missing person's case. Someone is kidnapping the numbers that can't be drained: we'll call them the immune.
啊哈！你的失踪人口案件。有人在绑架不能被吸干的数：我们称其为“免疫数”。
If you can identify the four immune who remain, perhaps you can get to them first and figure out what's going on. Who are the immune?
如果你找得到四个没被绑架的免疫数，也许就可以先拜访他们，弄明白发生的事情。谁是免疫数？
There are 4 one-digit immune: 2, 3, 5, and 7. All have already been kidnapped.
有四个一位数的免疫数：2、3、5、7，全部都已被绑架。
But every digit in all of the immune must be one of those four numbers; otherwise there would be a non-prime split possible.
但所有免疫数的各位数都必须是这四个数字之一，否则就可以切出一个非质数。
That means there are only these 16 candidates among the two-digit numbers. The ones that are prime must be immune.
这代表两位数的免疫数必然在这16位候选人之中，其中的质数一定是免疫数。
We can eliminate anything that ends in 2 or 5, as they'll always be divisible by 2 and 5.
我们可以删去尾数是2或5的数，因为他们总会被2或5整除。
This diagonal is also out, as they're divisible by 11. If the digits of a number add up to a multiple of 3, it's divisible by 3.
这条斜线的数也都出局了，因为会被11整除。若把某个数各个位数加总，得出的是3的倍数，那他本身也会被3整除。
So that eliminates 57 and 27, leaving these numbers. Which, upon double-checking, are, in fact, immune.
这样就会删去57和27，只留下这些数。经过双重检查，他们确实是免疫数。
We now have a strong starting point for searching three-digit numbers: any 2 consecutive digits must be on the list of the two-digit immune.
我们现在站在很好的起点，可以来搜寻三位数的免疫数：任两个连续的位数必须位在两位数的免疫数清单中。
Those all end in 3 and 7, so the only possibilities are these 8 options: the two-digit immune with additional 3s or 7s on their ends.
他们的尾数都是3或7，因此只有这八种可能性：在两位数的免疫数后面加上3或7。
3 can't follow 3, nor 7 follow 7. And once again, adding the digits reveals that 237 and 537 are divisible by 3.
3后面不能放3，7后面也不能放7。而且再一次，把各个位数相加就会发现237和537可以被3整除。
737 is 67 times 11, so that leaves just 373, which is, in fact, prime, and therefore immune. Could a four-digit number be immune?
737是67乘以11，这样就只剩373了，事实上373是质数，因此也是免疫数。可以有四位数的免疫数吗？
No, any consecutive three digits would have to be immune, and there's no immune three digit number that starts with a 7.
不行，任何连续的三个位数都必须是免疫数，但并没有三位数的免疫数第一个位数是7。
You rush out, but reach each home too late, until the only immune left is 373.
你冲了出去，但还是太晚抵达他们家，只剩373一个免疫数了。
You're in the nick of time to scare off her would-be kidnapper; not the vampire itself but a minion.
你在最后关头吓跑了想绑架她的人，不是吸血鬼本身，而是他的小喽啰。
373 explains that she and the other immune are the subjects of an ancient prophecy that designated them as vampire slayers.
373解释说她和其他免疫数是一个古老预言的主角，那个预言选定他们为吸血鬼猎人。
They'd sometimes gather and try to figure out what a vampire is, but no one had the slightest idea.
他们有时会聚在一起，试着弄清楚吸血鬼是谁，但没人有任何方向。
They found the idea of slaying things quite distasteful.
他们很厌恶杀人的想法。
You both trail her would-be kidnapper back to a foreboding castle.
你们两个跟踪试图绑架她的人，回到一座有着不祥预感的城堡。
There you release the other kidnapped numbers and confront the vampire himself.
在那里，你释放了其他被绑架的数，直接碰上了吸血鬼本人。
He's powerless before the slayers, but ever the pacifists, they round him up, return the lifeforce to his victims, and send him packing.
他在和平主义的吸血鬼猎人面前表现得不堪一击，他们将他围起来，把生命力还给被害人，并把他放逐。
Numberland is safe... for now.
数字王国安全了...目前是如此。
