#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 100000;
const int MMAX = 500000;

struct str{
    int first;
    int second;
};

int n, m, x, y;
vector < str > v[NMAX+1];
int trecut[MMAX+1];
int st[NMAX+1], sz;
int ans[MMAX+1],cnt;
int D[NMAX+1];

int main()
{
    fin >> n >> m;
    for(int i=1; i<=m; i++)
        fin >> x >> y, v[x].push_back( {y,i} ), v[y].push_back( {x,i} ), D[x]++, D[y]++;
    for(int i=1; i<=n; i++)
        if(D[i] % 2)
        {
            fout << -1;
            return 0;
        }
    st[++sz] = 1;
    while(sz)
    {
        bool gol = 1;
        int nod = st[sz];
        for(auto a : v[nod])
        {
            if(!trecut[a.second])
            {
                st[++sz] = a.first;
                trecut[a.second] = 1;
                gol = 0;
                break;
            }
        }
        if(sz && gol)
            sz--, ans[++cnt] = nod;
    }
    for(int i=cnt; i>1; i--)
        fout << ans[i] << ' ';
    return 0;
}