#include <iostream>

 #include <vector>

 #include <algorithm>

 #include <queue>

 #include <stack>

 #include <string>

 #include <fstream>

 #include <map>

 using namespace std;

 struct node {

     int data;

     struct node *left, *right;

     node() : data(), left(NULL), right(NULL) { }

     node(int d) : data(d), left(NULL), right(NULL) { }

 };

 void printleft(node *root) {

     if (!root) return;

     if (root->left) {

         cout << root->data << " ";

         printleft(root->left);

     }

     else if (root->right) {

         cout << root->data << " ";

         printleft(root->right);

     }

 }

 void printleaf(node *root) {

     if (!root) return;

     printleaf(root->left);

     if (!root->left && !root->right) cout << root->data << " ";

     printleaf(root->right);

 }

 void printright(node *root) {

     if (!root) return;

     if (root->right) {

         printright(root->right);

         cout << root->data << " ";

     }

     else if (root->left) {

         printright(root->left);

         cout << root->data << " ";

     }

 }

 void printboundary(node *root) {

     if (!root) return;

     cout << root->data << " ";

     printleft(root->left);

     printleaf(root);

     printright(root->right);

 }

 int main() {

     node *root = new node();

     root->left = new node();

     root->right = new node();

     root->left->left = new node();

     root->left->right = new node();

     root->right->right = new node();

     root->left->right->left = new node();

     root->left->right->right = new node();

     printboundary(root);

     return ;

 }