abcdefghijklmnopqrstuvwxyz
ok
b to a
goes back 1 letter
then b to d
skips 3 letters forward
then d to e
1 forward
e to h
skips 3 forward
h to g
goes 1 back
g to k
goes 3 forward
pattern seems to be
1back, 3 forward, 1 forward, 3 forward, repeat
so we are at 3 forward after than 1 back, so the next one is 1 forward
1 forward from k is l
the next letter is L