#include <bits/stdc++.h>
#define NMAX 100005
#define MMAX 500005
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int n,m;
int to[MMAX],from[MMAX];
stack<int>st;
vector< int > v[NMAX],sol;
int used[MMAX];
int cap;
int i;
int main()
{
    fin>>n>>m;
    while(m--)
    {
        int x,y;
        fin>>x>>y;
        v[x].push_back(m+1);
        v[y].push_back(m+1);
        from[m+1]=x;
        to[m+1]=y;
    }
    for(int i=1;i<=n;++i)
        if(v[i].size()%2==1)
    {
        fout<<-1;
        return 1;
    }
    st.push(1);
    while(!st.empty())
    {
        int k=st.top();
        if(v[k].size()==0)
        {
            st.pop();
            sol.push_back(k);
            continue;
        }
        int e=v[k].back();
        v[k].pop_back();
        if(!used[e])
        {
            used[e]=1;
            int next= from[e];
            if(k==next)
                next=to[e];
            st.push(next);
        }


    }
    for(i=0;i<=sol.size()-1;++i)fout<<sol[i]<<" ";
    return 0;
}