#include <fstream>
#include <vector>

using namespace std;

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

int n,m,i,x,y,grad[100005],f[500005],st[500005];
vector < pair <int, int> > L[500005];

int main()
{
    fin >> n >> m;
    for (i=1; i<=m; i++)
    {
        fin >> x >> y;
        L[x].push_back(make_pair(y, i));
        L[y].push_back(make_pair(x, i));
        grad[x]++; grad[y]++;
    }
    for (i=1; i<=n; i++)
        if (grad[i]%2 == 1)
        {
            fout << -1;
            return 0;
        }
    st[1] = 1; int k = 1;
    while (k != 0)
    {
        int nod = st[k];
        if (grad[nod] == 0)
        {
            if (k > 1)
                fout << nod << " ";
            k--;
            continue;
        }
        while (f[L[nod].back().second] == 1)
            L[nod].pop_back();
        int vecin = L[nod].back().first;
        f[L[nod].back().second] = 1;
        grad[nod]--; grad[vecin]--;
        L[nod].pop_back();
        st[++k] = vecin;
    }
    return 0;
}