#include <bits/stdc++.h>

using namespace std;

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

const int nMax = 500005;
int N, M, len;
int st[nMax], dr[nMax];
bool viz[nMax];
vector <int> L[nMax];
int ans[nMax], poz[nMax];

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

inline bool Euler()
{
    for(int i = 1; i <= N; i++)
        if(L[i].size() % 2)
            return false;
    return true;
}

inline void Dfs(int nod)
{
    int k;
    while(poz[nod] < L[nod].size())
    {
        k = L[nod][poz[nod]++];
        if(!viz[k])
        {
            viz[k] = true;
            Dfs(st[k] + dr[k] - nod);
        }
    }
    ans[++len] = nod;
}

inline void Solve()
{
    if(!Euler())
    {
        fout <<"-1\n";
        return;
    }
    Dfs(1);
    for(int i = 1; i <= len; i++)
        fout << ans[i] << " ";
}

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