Meet six robots:
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Alfie
2EB16C4F20A20
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Bettie
1859468147868
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Charlie
185AB8AC29D7A
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Dottie
0D6558A98BE52
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Eddie
2ACDC403A5A75
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Frankie
13F40E4D42644
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Each robot knows a code. Combined, the codes produce the posted coordinates. However, the cache is NOT at the posted coordinates! Turns out, some of the robots have malfunctioned.
Each robot can check at most two of the others. A working robot will give an accurate assessment of the one it checks. If, however, a robot is faulty, we cannot rely on anything it says.
Asking each robot to diagnose the others, we get the following answer:
Identify the minimum number of units that must be faulty and combine the codes from the remaining units to locate the cache.
Hide difficulty is 1.5.