#include <bits/stdc++.h>

using namespace std;
int n,m,x,y;
vector<pair<int,int> >edge;
vector<int>nod[100005],ans;
bool used[500005];
int main()
{
    ifstream fin("ciclueuler.in");
    ofstream fout("ciclueuler.out");
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        nod[x].push_back(i-1);
        nod[y].push_back(i-1);
        edge.push_back({x,y});
    }
    for(int i=1;i<=n;i++)
        if(nod[i].size()%2==1)
        {
            fout<<-1;
            return 0;
        }
    stack<int>stk;
    stk.push(1);
    while(!stk.empty())
    {
        int pos=stk.top();
        if(nod[pos].empty())
        {
            stk.pop();
            ans.push_back(pos);
            continue;
        }
        int e=nod[pos].back();
        nod[pos].pop_back();
        if(!used[e])
        {
            used[e]=true;
            stk.push(edge[e].first^edge[e].second^pos);
        }
    }
    for(int i=0;i<ans.size()-1;i++)
        fout<<ans[i]<<" ";
    return 0;
}