#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

const int nmx = 100002;

int n,m,grad[nmx];
vector <int> g[nmx],ciclu;
stack <int> st;

void citire()
{
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= m; ++i)
    {
        int nod1,nod2;
        scanf("%d %d", &nod1, &nod2);
        g[nod1].push_back(nod2);
        g[nod2].push_back(nod1);
        ++ grad[nod1];
        ++ grad[nod2];
    }
}

bool grade_bune()
{
    for(int i = 1; i <= n; ++i)
        if(grad[i] % 2 == 1)
            return 0;
    return 1;
}

void elimin_muchie(int nod1, int nod2)
{
    g[nod1].erase(find(g[nod1].begin(),g[nod1].end(),nod2));
    g[nod2].erase(find(g[nod2].begin(),g[nod2].end(),nod1));
}

void euler()
{
    st.push(1);

    while(not st.empty())
    {
        int nod = st.top();
        if(g[nod].size())
        {
            int nod_aux = g[nod].back();
            elimin_muchie(nod,nod_aux);
            st.push(nod_aux);
        }
        else
        {
           ciclu.push_back(nod);
           st.pop();
        }
    }
}

void afish()
{
    for(vector<int>::iterator it = ciclu.begin(); it != ciclu.end(); ++it)
        printf("%d ", *it);
    printf("\n");
}

int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    citire();
    if(not grade_bune())
        printf("-1");
    else
    {
        euler();
        afish();
    }
    return 0;
}