# You are given a list of dates in different formats. The formats can be of the form of 
# YYYY-DD-MM, DD/MM/YYYY, YYYY/MM/DD, DD-MM-YYYY, and so on.
#
# Given such a list, convert the dates to a format of YYYYMMDD, and return a list of dates 
# only if the original date was in the format of DD/MM/YYYY, YYYY/MM/DD, YYYY-MM-DD.
