# Who is the impostor?

C, the new head of a certain intelligence agency, is aware that there is an impostor hiding among the ranks.

In order to find the impostor, he has decided to ask all field agents to immediately link into a secure line, in order for C to preprocess them all.

The field agents call in by their call signs, as follows:

• 007
• 006
• 0012
• 008
• 005
• 0013
• 004

After compiling the list of agents, C notices an agent who cannot possibly exist, and immediately orders his arrest.

Who did C find?

I'll guess (due to the tag and other computery hints)

008

because if we take the numbers to be

octal (octal numbers are often represented with leading a 0)

clearly that one's not valid

• When you've been bitten by this enough times, this really jumps out at you :p – ffao Sep 30 '16 at 22:17
• @ffao Interesting -- do you often stick leading zeroes on numbers? – Rosie F Oct 1 '16 at 5:12
• @RosieF I've done it as an attempt to line up tables and calculations, only to have the whole program blow up. – ffao Oct 1 '16 at 13:38