#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int nmax = 500005;
int N,M;
bool v[nmax];
int st[nmax],dr[nmax];
vector < int > L[nmax];
vector < int > ans;

inline void Read()
{
    int i;
    fin >> N >> M;
    for(i = 1; i <= M; i++)
    {
        fin >> st[i] >> dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
}


inline bool Euler()
{
    int i;
    for(i = 1; i <= N; i++)
        if(L[i].size() & 1) return false;
    return true;
}

inline void DFS(int nod)
{
    for(auto it : L[nod])
    {
        if(!v[it])
        {
            v[it] = true;
            DFS(st[it] + dr[it] - nod);
        }
    }
    ans.push_back(nod);
}


inline void Solve()
{
    if(!Euler()) fout << "-1\n";
    else
    {
        DFS(1);
        ans.pop_back();
        for(auto it : ans) fout << it << " ";
    }
}


int main()
{
    Read();
    Solve();
    return 0;
}