I'd create an object with the following arrays as attributes: @seq, @lbl1, @lbl2, @lbl3, @lbl4, @con. Each element of each array is one letter.

At that point, it's fairly simple to write a method to iterate through the desired length and dump the total count of each possible LBL letter into a temporary hash, find the largest value of those, and write that letter out into the same position for @con.