#include <fstream>
#include <vector>

using namespace std;

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

int n, m, st[MMAX], dr[MMAX], ap[MMAX];
bool viz[MMAX];
vector<int> sol, G[NMAX];

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

void citire()
{
    fin >> n >> m;
    for(int i = 1; i <= m; ++i)
    {
        fin >> st[i] >> dr[i];
        G[st[i]].push_back(i);
        G[dr[i]].push_back(i);
    }
}

bool esteEulerian()
{
    for(int i = 1; i <= n; ++i)
        if(G[i].size() & 1) return 0;
    return 1;
}

void dfs(int k)
{
    while(ap[k] < G[k].size())
    {
        int i = G[k][ap[k]++];
        if(!viz[i])
        {
            viz[i] = 1;
            dfs(st[i] + dr[i] - k);
        }
    }
    sol.push_back(k);
}

void solutie()
{
    if(!esteEulerian())
    {
        fout << "-1";
        return;
    }
    dfs(1);
    for(const auto &x : sol)
        fout << x << ' ';
}

int main()
{
    citire();
    solutie();
    return 0;
}