#include <iostream>
#include <fstream>
#include <vector>
#include <set>
#include <deque>

using namespace std;

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

const int NMAX = 1e5+5;
const int MMAX = 5e5+5;

int n,m;
bool v[MMAX];
vector <pair<int ,int> >a[NMAX];

void dfs(int x)
{
    while(a[x].size() and v[a[x].back().second])
        a[x].pop_back();
    for(auto i:a[x])
        if(!v[i.second])
        {
            v[i.second]=true;
            dfs(i.first);
        }
    fout << x << " ";
}
int main()
{

    fin >> n >> m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin >> x >> y;
        a[x].push_back({y,i});
        a[y].push_back({x,i});
    }
    for(int i=1;i<=n;i++)
        if(a[i].size()%2)
        {
            fout << -1;
            return 0;
        }
    dfs(rand()%n + 1);
    return 0;

}