#include <iostream>
#include <vector>
#include <algorithm>

typedef int                             Node;
typedef std::vector<std::vector<Node>>  List;

void dfs(List& neighbours, std::vector<bool>& visited, Node u)
{
    visited[u] = true;

    for (Node v : neighbours[u]) {
        if (!visited[v]) { 
            dfs(neighbours, visited, v);
        }
    }
}

void erase_edge(List& neighbours, Node u, Node v) 
{
    neighbours[u].erase(find(neighbours[u].begin(), neighbours[u].end(), v));
    neighbours[v].erase(find(neighbours[v].begin(), neighbours[v].end(), u));
}

bool is_valid(List& neighbours, int u, int v) 
{
    // Ako je (u,v) jedina grana uzimamo nju
    if (neighbours[u].size() == 1) {
        return true;
    }

    // Ako ne posotji grane
    if (neighbours[u].empty() || neighbours[v].empty()) {
        return false;
    }

    std::vector<bool> visited(neighbours.size(), false);

    erase_edge(neighbours, u, v);

    dfs(neighbours, visited, u);

    neighbours[u].push_back(v);
    neighbours[v].push_back(u);

    if (visited[v]) {
        return true;
    }

    return false;
}

void fleury(List& neighbours, std::vector<int>& euler, int u) 
{
    for (int v : neighbours[u]) {
        if (is_valid(neighbours, u, v)) {
            euler.push_back(v);
            erase_edge(neighbours, u, v);
            fleury(neighbours, euler, v);
        }
    }
}

void print_euler(List& neighbours) 
{
    int num_odd = 0;
    int odd = 0;
    for (Node u = 0; u < neighbours.size(); u++) {
        if (neighbours[u].size() % 2 != 0) {
            num_odd++;
            odd = u;
        }
    }

    if (num_odd != 0 && num_odd != 2) {
        std::cout << "Ne postoji Ojler" << std::endl;
        return;
    }

    std::vector<Node> euler;
    if (num_odd == 2) {
        euler.push_back(odd);
        fleury(neighbours, euler, odd);
    } else {
        euler.push_back(0);
        fleury(neighbours, euler, 0);
    }

    for (Node u : euler) {
        std::cout << u << " ";
    }
    std::cout << std::endl;
}

int main(void)
{
    List neighbours = {
        {1, 2},
        {0, 2},
        {0, 1, 3},
        {2}
    };

    print_euler(neighbours);
    
    return 0;
}