#include <bits/stdc++.h>
using namespace std;
struct TreeNode{
int data;
TreeNode* left;
TreeNode* right;
TreeNode(int val):left(nullptr),right(nullptr),data(val){};
};

vector<vector<int>>level(TreeNode* root){
	vector<vector<int>>ans;
	queue<TreeNode*>q;
	if(root == nullptr){
		return ans;
	}
	
	q.push(root);
	
	while(!q.empty()){
		int size = q.size();
		vector<int>lvl;
		for(int i = 0;i< size;i++){
			auto u=q.front();q.pop();
			lvl.push_back(u->data);
			if(u->left){
				q.push(u->left);
			}
			
			if(u->right){
				q.push(u->right);
			}
		}
		ans.push_back(lvl);
	}
	return ans;
}
TreeNode* buildTree(){
	int x;cin>>x;
	if(x==-1)return nullptr;
	TreeNode* root = new TreeNode(x);
	queue<TreeNode*>q;
	q.push(root);
	
	while(!q.empty()){
		auto u = q.front();
		q.pop();
		
		if(cin>>x && x!= -1){
			u->left = new TreeNode(x);
			q.push(u->left);
		}
		
			if(cin>>x && x!= -1){
			u->right = new TreeNode(x);
			q.push(u->right);
		}
	}
	return root;
}
int main() {
    TreeNode* root = buildTree();
    vector<vector<int>>ans = level(root);
   // Clean range-based iteration
    for (const auto& lvl : ans) {
        for (int val : lvl) {
            cout << val << " ";
        }
        cout << "\n";
    }
	return 0;
}