import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;
public class Main {
public static void main(String[] argv) throws Exception {
}
public static String containsValue(Preferences node, String value) {
try {
String[] keys = node.keys();
for (int i = 0; i < keys.length; i++) {
if (value.equals(node.get(keys[i], null))) {
return keys[i];
}
}
} catch (BackingStoreException e) {
}
return null;
}
}