#include <bits/stdc++.h>

using namespace std;

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

vector <vector<pair<int,int>>> a;
vector <int> gasit;
vector <int> r;
void dfs(int nod)
{
    while(!a[nod].empty())
    {
        auto x=a[nod].back();
        a[nod].pop_back();
        if(!gasit[x.second])
        {
            gasit[x.second]=1;
            dfs(x.first);
        }
    }
    r.push_back(nod);
}
int main()
{
    int n,m;
    in>>n>>m;
    a.resize(n+1);
    vector <int> grad(n+1);
    gasit.resize(m+1);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        in>>x>>y;
        a[x].push_back({y,i});
        a[y].push_back({x,i});
        grad[x]++;
        grad[y]++;
    }
    for(int i=1;i<=n;i++)
    {
        if(grad[i]%2==1)
        {
            out<<-1;
            return 0;
        }
    }
    dfs(1);
    if(r.size()!=m+1)
    {
        out<<-1;
        return 0;
    }
    for(int i=0;i<m;i++)
    {
        out<<r[i]<<" ";
    }
    return 0;
}