Growing and Shrinking Potions

There are two types of potions:

1. Growing potion: "A"
2. Shrinking potion: "B"

• If "A" immediately follows a digit, add 1 to the digit.
• If "B" immediately follows a digit, subtract 1 from the digit.

Create a function that returns a string according to these rules, removing the potions once they've been consumed.

Examples

after_potion("3A78B51") ➞ "47751"
# 3 grows to 4, 8 shrinks to 7

after_potion("9999B") ➞ "9998"

after_potion("9A123") ➞ "10123"

after_potion("567") ➞ "567"

Notes

• Digits that do not have a potion on their immediate right should be left alone.
• A digit will always either be followed by zero or exactly 1 potion.