#include <fstream>
#include <vector>
using namespace std;
ifstream cin ("ciclueuler.in");
ofstream cout ("ciclueuler.out");
int a[500003],b[500003],ok[500003];
vector<int>v[100003];
int okt=0;
int dfs (int pz)
{
    for(int i=v[pz].size()-1;i>=0;--i)
    {
        int m=v[pz][i];
        v[pz].pop_back();
        if(ok[m])
            continue;
        ok[m]=1;
        int nn=(pz^a[m]^b[m]);
        dfs(nn);
    }
    if(okt)
        cout<<pz<<' ';
    okt=1;
}
int main()
{
    ios_base::sync_with_stdio(false);
    long long t,i,j,k=0,m;
    long long x1,y1,x2,y2,pas,val,n;
    cin>>n>>m;
    for(i=1;i<=m;++i)
    {
        cin>>a[i]>>b[i];
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
    }
    for(i=1;i<=n;++i)
    {
        if(v[i].size()&1)
        {
            cout<<-1;
            return 0;
        }
    }
    dfs(1);
    return 0;
}