#include <bits/stdc++.h>

using namespace std;

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

int n,m,i,x,y;
int from[500001],to[500001],used[500001];
vector <int> v[100001],ans;
stack <int> stk;


int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(i);
        v[y].push_back(i);
        from[i]=x;to[i]=y;
    }
    for(i=1;i<=n;i++)
        if(v[i].size()%2==1)
    {
        fout<<-1;
        return 0;
    }

    stk.push(1);
    while(!stk.empty())
    {
        int nod=stk.top();
        if(!v[nod].empty())
        {
            int muc=v[nod].back();
            v[nod].pop_back();
            if(!used[muc])
            {
                stk.push(to[muc]^from[muc]^nod);
                used[muc]=true;
            }
        }
        else
        {
            ans.push_back(nod);
            stk.pop();
        }
    }
    for(int i=0;i<ans.size()-1;i++)
        fout<<ans[i]<<" ";
    return 0;
}