#include <bits/stdc++.h>

std :: ifstream in ("ciclueuler.in");

std :: ofstream out ("ciclueuler.out");

const int NMAX = 1e5 + 5;

int n;

int m;

int x;

int y;

std :: vector <std :: pair <int, int>> v[NMAX];

std :: bitset <5 * NMAX> visited;

std :: vector <int> path;

void dfs(int nod)
{
    while(!v[nod].empty())
    {
        x = v[nod].back().first;

        y = v[nod].back().second;

        v[nod].pop_back();

        if(visited[y] == false)
        {
            visited[y] = true;

            dfs(x);
        }
    }

    path.push_back(nod);
}

void dfss(int nod)
{
    for(auto i : v[nod])
    {
        if(visited[i.first] == false)
        {
            visited[i.first] = true;

            dfss(i.first);
        }
    }
}

bool check()
{
    visited[1] = true;

    dfss(1);

    for(int i = 1; i <= n; i ++)
    {
        if(visited[i] == false)
        {
            return false;
        }
    }

    visited &= 0;

    for(int i = 1; i <= n; i ++)
    {
        if(v[i].size() % 2)
        {
            return false;
        }
    }

    return true;
}

int main()
{

    in >> n >> m;

    for(int i = 1; i <= m; i ++)
    {
        in >> x >> y;

        v[x].push_back(std :: make_pair(y, i));

        v[y].push_back(std :: make_pair(x, i));
    }

    if(check() == false)
    {
        out << -1;

        return 0;
    }

    dfs(1);

    path.pop_back();

    for(int i = 1; i <= m; i ++)
    {
        if(visited[i] == false)
        {
            out << -1;

            return 0;
        }
    }

    for(int i : path)
    {
        out << i << " ";
    }

    return 0;
}