#include <fstream>
#include <algorithm>
#include <iomanip>
#include <vector>

#define pdd pair<double, double>
#define x first
#define y second
#define mkp make_pair
#define nMax 100003
#define pb push_back
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int n, m;
vector<int> G[nMax], Stck;
void read()
{
    int a, b;
    fin>>n>>m;

    for(int i=1;i<=m;i++)
    {
        fin>>a>>b;
        G[a].pb(b);
        G[b].pb(a);
    }
}
void euler()
{
    Stck.pb(1);

    while(Stck.size())
    {
        int node=Stck.back();
        if(G[node].size())
        {
            int fiu=G[node].back();
            G[node].pop_back();
            G[fiu].erase(find(G[fiu].begin(), G[fiu].end(), node));
            Stck.pb(fiu);
        }
        else
        {
            fout<<node<<" ";
            Stck.pop_back();
        }
    }
}
void solve()
{
    for(int i=1;i<=n;i++)
    {
        if(G[i].size() & 1)
        {
            fout<<-1;
            return;
        }
    }

    euler();
}
int main()
{
    read();
    solve();
    return 0;
}