Suppose a hash # represents the BACKSPACE key being pressed. Write a function that transforms a string containing # into a string without any #.

Examples

erase("he##l#hel#llo") ➞ "hello"

erase("major# spar##ks") ➞ "majo spks"

erase("si###t boy") ➞ "t boy"

erase("####") ➞ ""

Notes

• In addition to characters, backspaces can also remove whitespaces.
• If the number of hashes exceeds the previous characters, remove those previous characters entirely (see example #3).
• If there only exist backspaces, return an empty string (see example #4).