#include <fstream>
#include <list>
#include <algorithm>

#define NMAX 100010

using namespace std;

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

int n, m, i, j, vf, x, y;
int stiva[NMAX*5];
list<int> l[NMAX];

int main()
{
    fin >> n >> m;
    for(i = 1; i <= m; ++i)
    {
        fin >> x >> y;
        l[x].push_back(y);
        l[y].push_back(x);
    }
    for(i = 1; i <= n; ++i)
        if(l[i].size() % 2 == 1)
    {
        fout << "-1" << '\n';
        return 0;
    }
    vf = 1;
    stiva[vf] = 1;
    while(vf > 0)
    {
        x = stiva[vf];
        while(!l[x].empty())
        {
            y = l[x].front();
            l[x].pop_front();
            l[y].erase(find(l[y].begin(), l[y].end(), x));
            vf++;
            stiva[vf] = y;
            x = y;
        }
        fout << stiva[vf--] << ' ';
    }
    return 0;
}