In this task, you are given a string of characters. You need to remove duplicate characters from the string if any, and return the resulting string.

osRkjysAYNKHZYSWIEORxnZJWf
osRkjyAYNKHZSWIEOxnJf

GfjMUpfjwqpWyIVlTdNIOYoJND
GfjMUpwqWyIVlTdNOYoJD

CwQBJjXAtwxJSVmjIScuDA

CwQBJjXAtxSVmIcuD