The Biggest Jump Between Two Days

Your channel's subscriber count is logged daily — which morning did it jump up the most? 📈

You get a list of daily counts (at least two). Print the biggest one-day INCREASE. If the count only ever fell, print the least-bad change (it may be negative).

Example:

Input: counts = [100, 120, 90, 150] Output: 60

The day-to-day changes are 20, -30, 60 — the biggest jump is 60, from 90 to 150.