#include <bits/stdc++.h>

using namespace std;
const int N = 5e5 + 5;
struct edge { int u, v; } e[N];
int adj(int u, int id) { return e[id].u ^ e[id].v ^ u; }
bool vis[N];
vector <int> g[N];
vector <int> tour;

void dfs(int u) {
    while(!g[u].empty()) {
        int id = g[u].back();
        if(!vis[id]) {
            int v = adj(u, id);
            vis[id] = true;
            g[u].pop_back();
            dfs(v);
        } else g[u].pop_back();
    }
    tour.push_back(u);
}

int main()
{
    ifstream cin("ciclueuler.in");
    ofstream cout("ciclueuler.out");
    int n, m;
    cin >> n >> m;
    for(int i = 0, u, v; i < m; i++) {
        cin >> u >> v;
        e[i] = {u, v};
        g[u].push_back(i);
        g[v].push_back(i);
    }
    dfs(1);
    tour.pop_back();
    if(tour.size() != m)
        cout << "-1";
    else for(int x : tour)
        cout << x << " ";
    return 0;
}