import java.io.File;

class Main {
    String getParent(String path) {
        if (path == null) {
            throw new NullPointerException();
        }
        String path1 = fs.normalize(path);
        int prefixLength = fs.prefixLength(path1);
        int index = path1.lastIndexOf(File.separatorChar);
        if (index < prefixLength) {
            if ((prefixLength > 0) && (path1.length() > prefixLength))
                return path1.substring(0, prefixLength);
            return null;
        }
        return path1.substring(0, index);
    }
}