import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String s = "sabca";
		System.out.println(f(s.toCharArray()));
		System.out.println(g(new StringBuilder(s)));
	}
	public static String f(char[]s){String t="";for(char c:s)t+=t.contains(c+"")?"":c;return t;}
	public static String g(StringBuilder s){return new StringBuilder(s.reverse().toString().replaceAll("(?s)(.)(?=.*\\1)", "")).reverse().toString();}
}