public class klammern {
    public static void main(String [] args) {
        List l=new List('(',')',
                        new List('[',']',
                                 new List('{','}',
                                          new List('<','>',
                                                   null))));
        System.out.println(l);
    }
}
class List {
    char open;
    char close;
    List inner; // next
    List(char o, char c, List i) {
        open = o;
        close = c;
        inner = i;
    }
    public String toString() {
        return open+(inner==null ? "" : inner.toString())+close;
    }
}