You are given a string, str, of length N consisting of lowercase letters of alphabet. You have to remove all those characters from str which have already appeared in it, i.e., you have to keep only first occurance of each letter.
First line of input contains a string str of length N.
A string with removed characters as described in the problem.
1 <= N <= 30000 str will contain only lowercase letters ('a'-'z').
Sample Input #00
Sample Output #00
Sample Input #01
Sample Output #01
Explanation Test Case #00: Here you have to remove 'a' at index 1 (0 based indexing) because it has already appeared at index 0. Test Case #01: Here you have to remove 'c' from index 1, 6 and 7, because 'c' has already appeared at index 0. Similarly you have to remove 'b' from index 4 and 'a' from index 5.