#include <bits/stdc++.h>
using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int nMax = 1e5 + 1;
const int mMax = 5e5 + 1;
int n, m;
vector<pair<int,int>> graph[nMax];
vector<int> cycle;
bitset<mMax> v;

void euler(int node)
{
    while(!graph[node].empty())
    {
        int next = graph[node].back().first;
        int edge = graph[node].back().second;
        graph[node].pop_back();
        if(v[edge])
            continue;
        v[edge] = 1;
        euler(next);
    }
    cycle.push_back(node);
}

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

    fin >> n >> m;
    for(int i = 1; i <= m; ++i)
    {
        int x, y;
        fin >> x >> y;
        graph[x].push_back({y, i});
        graph[y].push_back({x, i});
    }
    for(int i = 1; i <= n; ++i)
        if(graph[i].size() % 2)
        {
            fout << -1;
            return 0;
        }
    euler(1);
    for(int i: cycle)
        fout << i << " ";

    fin.close();
    fout.close();
    return 0;
}