The Warmed Up challenge gives us the plan and simple question:

What is 0x3D (base 16) in decimal (base 10)?

So we need to decode the hexadecimal (we know that because base16 is hexadecimal, (characters 1 to 10 + A to F) Value 0x3D into the common and human readable Form. The hint just tells us to remember the general syntax of the flags: picoCTF{}.

As we are lazy we just slam “Hexadecimal to Decimal Converter” into good old google and get plenty of results. The first page delivers the solution: 61
(i took https://www.rapidtables.com/convert/number/hex-to-decimal.html)

Submit the solution and…. Hoooooray, another 50 Points!

(Note: We just could have used good old cyberchef and probably a ton of other sites to solve this)