#include <bits/stdc++.h>
#define pb push_back
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
const int N=100009,M=500009;
int n,m;
int d[M],from[M],to[M],sol[M];
vector <int> v[N];
stack <int> sk;
void solve()
{
    for(int i=1;i<=n;i++)
        if(v[i].size()%2)
        {
            fout<<-1;
            return ;
        }
    sk.push(1);
    while(!sk.empty())
    {
        int nod=sk.top();
        if(!v[nod].empty())
        {
            int muchie=v[nod].back();
            v[nod].pop_back();
            if(!d[muchie])
            {
                d[muchie]=1;
                if(from[muchie]==nod)
                    sk.push(to[muchie]);
                else
                    sk.push(from[muchie]);
            }
        }
        else
        {
            sk.pop();
            sol[++sol[0]]=nod;
        }
    }
    for(int i=1;i<sol[0];i++)
        fout<<sol[i]<<" ";
}
int main()
{
    fin.sync_with_stdio(false);
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        v[x].pb(i);
        v[y].pb(i);
        from[i]=y,to[i]=x;
    }
    solve();
    return 0;
}