#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;
ifstream f("sortaret.in");
ofstream g("sortaret.out");
struct nod{int val; int poz;} aux;
int n,m,i,j,sol[500005],x,y,nr,ok,viz[500005],stiva[500005],vf;
vector<nod> v[100005];

void euler()
{
    int i=v[i].size();
    nod aux;
    while(vf>0)
    {
        x=stiva[vf];
        while(!v[x].empty() && viz[v[x].back().poz]==1) v[x].pop_back();
        if(!v[x].empty())
        {
            stiva[++vf]=v[x].back().val;
            viz[v[x].back().poz]=1;
            v[x].pop_back();
        }
        else
        {
            if(vf>1) sol[++nr]=x;
            vf--;
        }
    }
}

int main()
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        aux={y,i};
        v[x].push_back(aux);
        aux={x,i};
        v[y].push_back(aux);
    }
    ok=1;
    for(i=1;i<=n;i++) if(v[i].size()%2==1) ok=0;
    if(ok)
    {
        nr=0;
        vf=1;
        stiva[1]=1;
        euler();
        for(i=1;i<=nr;i++) g<<sol[i]<<' ';
    }
    else g<<-1<<'\n';
    return 0;
}