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

using namespace std;

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

vector <int> v[100001];
int sol[100001],n,m,nr;

void euler(int start)
{
    int a,i,k;
    a=start;
    while(!v[a].empty())
    {
        i=v[a][0];
        v[a].erase(v[a].begin());
        k=0;
        while(v[i][k]!=a)
            k++;
        v[i].erase(v[i].begin()+k);
        euler(i);
    }
    sol[nr]=a;
    nr++;
}

int main()
{
    int x,y;
    bool check=true;
    in>>n>>m;
    for(int i=0; i<m; i++)
    {
        in>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for(int i=1; i<=n; i++)
    {
        if(v[i].size()%2!=0)
            check = false;
    }
    if(check)
    euler(1);
    else out<<-1;
    if(check)
    for(int i=0; i<nr; i++)
    {
        out<<sol[i]<<" ";
    }
    return 0;
}