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

using namespace std;

#define MAX 100010

typedef vector < int > ::iterator iter;
vector < int > g[MAX];

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

bool viz[MAX];
int n,m,f[MAX],st[5*MAX],dr;

void df(int nod)
{
    viz[nod]=1;
    for(iter it=g[nod].begin();it!=g[nod].end();it++)
        if(!viz[*it])
            df(*it);
}

int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        f[x]++;
        f[y]++;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    df(1);
    bool ok=1;
    for(int i=1;i<=n;i++)
        if(f[i]%2==1 || !viz[i])
            ok=0;
    if(ok==0)
    {
        fout<<"-1\n"<<endl;
        return 0;
    }
    st[++dr]=1;
    int k=0;
    while(dr)
    {
        int nod=st[dr];
        if(g[nod].size()==0)
        {
            if(++k<=m)
                fout<<st[dr]<<" ";
            dr--;
        }
        else
        {
            int v=g[nod][0];
            st[++dr]=v;
            swap(g[nod][0],g[nod][g[nod].size()-1]);
            g[nod].pop_back();
            for(iter it=g[v].begin();it!=g[v].end();it++)
            {
                if(*it==nod)
                {
                    g[v].erase(it);
                    break;
                }
            }
        }
    }
    fin.close();
    fout.close();
    return 0;
}