/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class CBTInserter {
public:
    TreeNode* root;
    queue<TreeNode*> par;
    queue<TreeNode*> now;

    CBTInserter(TreeNode* root) {
        this->root = root;
        if (!root) return;
        if (root && !root->left) {
            now.push(root);
            return;
        }
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            unsigned int len = q.size();
            par = q;
            queue<TreeNode*> t;
            while (!q.empty()) {
                auto node = q.front();
                if (node->left) t.push(node->left);
                if (node->right) t.push(node->right);
                q.pop();
            }
            q = t;
            if (!t.empty() && t.size() != len * 2)
                now = par;
        }
        if (now.empty()) {
            now = par;
            return;
        }
        par = now;
        while (!par.empty()) {
            if (par.front() && par.front()->left) now.push(par.front()->left);
            if (par.front() && par.front()->right) now.push(par.front()->right);
            par.pop();
        }
        while (1) {
            auto node = now.front();
            if (node->left && node->right) {
                printf("%d %d\n", node->left->val, node->right->val);
                now.pop();
            }
            else break;
        }
    }
    
    int insert(int val) {
        TreeNode* node = new TreeNode(val);
        auto n = now.front();
        if (!n->left) {
            printf("%d\n", n->val);
            n->left = node;
        }
        else if (!n->right) {
            printf("%d\n", n->val);
            n->right = node;
            now.pop();
        }
        now.push(node);
        return n->val;
    }
    
    TreeNode* get_root() {
        return root;
    }
};

/**
 * Your CBTInserter object will be instantiated and called as such:
 * CBTInserter* obj = new CBTInserter(root);
 * int param_1 = obj->insert(val);
 * TreeNode* param_2 = obj->get_root();
 */