Given a string, return if a given letter always appears immediately before another given letter.

Worked Example

best_friend("he headed to the store", "h", "e") ➞ True

# All occurences of "h": ["he", "headed", "the"]
# All occurences of "h" have an "e" after it.
# Return True

Examples

best_friend("he headed to the store", "h", "e") ➞ True

best_friend("i found an ounce with my hound", "o", "u") ➞ True

best_friend("we found your dynamite", "d", "y") ➞ False

Notes

• Don't count letters with spaces between them (example #3).
• All sentences will be given in lowercase.