import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.Collections;
import java.util.Arrays;
public class MyClass {
public static void main(String args[]) {
String s = "java php php c# php java x y x y y y python q w";
List<String> list = Arrays.asList(s.split(" "));
Set<String> set_without_duplicates = new HashSet<String>(list);
for (String word : set_without_duplicates) {
if (Collections.frequency(list, word) == 1)
System.out.println(word);
}
}
}
/*
run:
c#
python
q
w
*/