View Compilation Error

0_0_28889364_9383\Main.java:38: 错误: 程序包org.smallnico.hdu.Main.CartesianTree不存在
    public static int area(org.smallnico.hdu.Main.CartesianTree.Node n) {
                                                               ^
0_0_28889364_9383\Main.java:43: 错误: 程序包org.smallnico.hdu.Main.CartesianTree不存在
    public static int dfs(org.smallnico.hdu.Main.CartesianTree.Node n, int count) {
                                                              ^
0_0_28889364_9383\Main.java:26: 错误: 程序包org.smallnico.hdu.Main.CartesianTree不存在
            List<org.smallnico.hdu.Main.CartesianTree.Node> nodes = t.getList();
                                                     ^
0_0_28889364_9383\Main.java:28: 错误: 程序包org.smallnico.hdu.Main.CartesianTree不存在
            for(org.smallnico.hdu.Main.CartesianTree.Node n: nodes) {
                                                    ^
4 个错误