This is a fairly simple challenge. Given a lower-case word, you must "interpolate" between letters. Here's some examples to hopefully clarify this:
Between letters you must add, in alphabetical order, the letters between those two letters. So if you have
ad, you must output
abcd. If you are given
da, you must output
If the letters are next to each other in the alphabet, nothing happens:
Assume the input contains a lower-case word consisting of ASCII letters only; no spaces, symbols, etc. The input is also never empty.
Lowest byte count wins; this is code-golf. If you have any questions please comment.