Thanks a lot!

1. Filter out non-hexadecimal characters (just leaving hexadecimal) = "redlionfish"   ----> ["e", "d", "f"]
2. Convert each hexadecimal character to denary/decimal (base 10)   = ["e", "d", "f"] ----> [14, 13, 15]
3. XOR together each integer. Do this by XORing the first two
   integers then the result of this is the product of the next XOR  =  [14, 13]    --->  14^13  ---> 3
                                                                       [3, 15]     --->  3^15   ---> 12

I don't understand this "e,d,f -> XOR"
I know XOR like this a ^ b... e,d,f.... I don't know...

You made my day, thanks!

I think this instructions are wrong. The longest element can not including to result :((