Deoxyribonucleic acid is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. A DNA molecule consists of two strands that wrap around each other to resemble a twisted ladder whose sides, made of sugar and phosphate molecules, are connected by rungs of nitrogen-containing chemicals called bases. Each strand is a linear arrangement of repeating similar units called nucleotides. Each nucleotide is composed of a nitrogen-containing nucleobase—either guanine (G), adenine (A), thymine (T), or cytosine (C). The particular order of the bases arranged along the sugar-phosphate backbone is called the DNA sequence; the sequence specifies the exact genetic instructions required to create a particular organism with its own unique traits.

For this mission, we want to compare DNA strands and find the longest common base subsequence in the two strands. Subsequences are not required to occupy consecutive positions within the original sequences and letters can be placed at varying distances between each other. These strands can be represented as strings consisting of the letters "ACGT". For example the longest common sequence for strands "ACGTC" and "TTACTC" is "ACTC".

You are given two strand descriptions and you should find the longest common subsequence (not the substring). If we find several “longest” sequences with equal length, then return each of them as a string where these sequence are written in lexicographical order separated by commas. For example, for "CGCTA" and "TACCG" we found three sequences "CG", CC and "TA", so the result is "CC,CG,TA". If the given sequences don't have a common sequence then return an empty string.

Input: Two arguments. Base sequences as strings.

Output: The common longest sequence or sequences as a string.

How it is used: Bioinformatic scientists often use programming skills to model and examine DNA sequences in a lab. With the concepts from this mission, you can create the foundation of such a tool.

Precondition:
all(0 < len(seq) ≤ 64 and all(x in "ACGT" for x in seq) for seq in args)