/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
 
    Scanner fileIn = new Scanner(System.in);
    List<String> list = new ArrayList<>();
    while (fileIn.hasNext()) {
        list.add(fileIn.next());
    }           
    Collections.sort(list);
    int pos = 0;
    while (pos != list.size()) {
    	int next = pos+1;
    	while (next != list.size() && list.get(pos).equals(list.get(next))) {
    		next++;
    	}
    	if (next == pos+1) {
    		System.out.println(list.get(pos));
    	}
    	pos = next;
    }
 
	}
}

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