#include <fstream>
#include <vector>
#include <algorithm>
#define dim 100001
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector <int> G[dim];
vector <int> Stiv;
int node,fiu,a,b,i,n,m;
void euler()
{
    Stiv.push_back(1);
    while(Stiv.size())
    {
        node=Stiv.back();
        if(G[node].size())
        {
            fiu=G[node].back();
            G[node].pop_back();
            G[fiu].erase(find(G[fiu].begin(),G[fiu].end(),node));
            Stiv.push_back(fiu);
        }
        else
        {
            fout<<node<<" ";
            Stiv.pop_back();
        }
    }
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    for(i=1;i<=n;i++)
        if(G[i].size()&1)
        {
            fout<<-1;
            return 0;
        }
    euler();
    return 0;
}