#include <bits/stdc++.h>
#define Dmax 100005

using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
struct muchie
{
    int first,second;
    bool third;
};
int n,m;
vector<int>G[Dmax];
vector<muchie>M;



int main()
{
    f>>n>>m;
    for(int i = 1; i <= m; i++)
    {
        int x,y;
        f>>x>>y;
        M.push_back({x,y,false});
        G[x].push_back(i);
        G[y].push_back(i);
    }

    for(int i = 1; i <= n; i++)
        if(G[i].size() & 1)
    {
        g<<"-1\n";
        return 0;
    }

    stack<int>S;
    vector<int>sol;
    S.push(1);
    while(!S.empty())
    {
        int nod = S.top();
        if(G[nod].empty())
        {
            sol.push_back(nod);
            S.pop();
        }
        else
        {
            int muchie = G[nod].back();
            G[nod].pop_back();
            muchie--;
            if(!M[muchie].third)
            {
                M[muchie].third = true;
                if(M[muchie].first == nod)
                    S.push(M[muchie].second);
                else
                    S.push(M[muchie].first);
            }
        }
    }
    for(vector<int>::iterator it = sol.begin(); it < sol.end() - 1; it++)
        g<<*it<<" ";

    return 0;
}