#include <iostream>
#include <queue>
#include <algorithm>
#include <set>
#include <map>
#include <stack>
#include <vector>
#include <string>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <cmath>
#include <iomanip>
using namespace std;

int n, m;
vector<vector<pair<int,int>>> adj; // (neighbor, edge_id)
vector<bool> used; // tracks if edge has been used
vector<int> res;

void ReadData() {
    cin >> n >> m;
    adj.assign(n, {});
    used.assign(m, false);

    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        u--; v--; // convert to 0-indexed
        adj[u].push_back({v, i});
        adj[v].push_back({u, i}); // undirected edge
    }
}

// Hierholzer's algorithm using recursive DFS
void dfs(int v) {
    while (!adj[v].empty()) {
        auto [u, eid] = adj[v].back();
        adj[v].pop_back();
        if (used[eid]) continue;
        used[eid] = true;
        dfs(u);
    }
    res.push_back(v); // add vertex after all edges are used
}

void Solve() {
    int start = -1;

    // choose start vertex: odd degree if exists, else any with edges
    for (int i = 0; i < n; i++) {
        if (adj[i].size() % 2 == 1) {
            start = i;
            break;
        }
    }
    if (start == -1) {
        for (int i = 0; i < n; i++) {
            if (!adj[i].empty()) {
                start = i;
                break;
            }
        }
    }

    if (start == -1) { // no edges at all
        cout << "-1\n";
        return;
    }

    dfs(start);

    if ((int)res.size() != m + 1) {
        cout << "-1\n"; // not all edges were used
        return;
    }

    // output the path in correct order
    for (int i = res.size() - 1; i >= 0; i--) {
        cout << res[i] + 1 << " ";
    }
    cout << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    ReadData();
    Solve();

    return 0;
}