Remove Duplicates From String

You are given a string (STR) of length N, consisting of only the lower case English alphabet.

Your task is to remove all the duplicate occurrences of characters in the string.

For Example:

If the given string is:
abcadeecfb

Then after deleting all duplicate occurrences, the string looks like this:
abcdef

Input Format:

The only input line contains a string (STR).

Output Format:

Print the string after removing all the duplicate occurrences.

Constraints:

1 <= N <= 4*10^5

Time Limit: 1sec

Sample Input 1:

abcadeecfb

Sample Output 1:

abcdef

Sample Input 2:

zzzzzxx

Sample Output 2:

zx