#include <iostream>
#include <fstream>
#include <stack>
#include <vector>
using namespace std;
ifstream f ("ciclueuler.in");
ofstream g("ciclueuler.out");
int n,m;
vector<int>adiacenta[100001];
vector<int>rasp;
bool viz[500001];
pair<int,int>muchii[500001];
int grade[100001];
stack<int>st;
int main()
{
    f >> n>> m;
    for(int i = 1;i<=m;i++)
    {
        int x,y;
        f >> x >> y;
        adiacenta[x].push_back(i);
        adiacenta[y].push_back(i);
        muchii[i]={x,y};
        grade[x]++;
        grade[y]++;
    }
    for(int i =1;i<=n;i++)
    {
        if(grade[i]%2==1)
        {
            g << -1;
            return 0;
        }
    }


    st.push(1);
    while(!st.empty())
    {
        int curent = st.top();
        if(adiacenta[curent].size()==0)
        {
            rasp.push_back(curent);
            st.pop();
            continue;
        }
        if(viz[adiacenta[curent].back()])
        {
            adiacenta[curent].pop_back();
            continue;
        }
        if(!viz[adiacenta[curent].back()])
        {
            viz[adiacenta[curent].back()] = 1;
           int muchie =  adiacenta[curent].back();
           adiacenta[curent].pop_back();
           if(muchii[muchie].first==curent)
            st.push(muchii[muchie].second);
           else
            st.push(muchii[muchie].first);

        }
    }
    for(auto x:rasp)
        g << x<< " ";
}