#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int nmax = 500005;
int N,M,st[nmax],dr[nmax],ans[nmax];
bool used[nmax];
vector < int > L[nmax];
inline void Read()
{
    fin >> N >> M;
    for(int i = 1; i <= M; i++)
    {
        fin >> st[i] >> dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
}
inline bool Este_Euler()
{
    for(int 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(!used[it])
        {
            used[it] = true;
            DFS(st[it] + dr[it]-nod);
        }
    }
    ans[++ans[0]] = nod;
}

int main()
{
    Read();
    if(!Este_Euler()) fout << "-1\n";
    else
    {
        DFS(1);
        for(int i = 1; i < ans[0]; i++) fout << ans[i] << " ";
        fout << "\n";
    }
    fout.close();
    return 0;
}