#include <fstream>
#include <vector>
#include <algorithm>

#define nMax 100001
#define pb push_back

using namespace std;

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

int n, m, viz[nMax], grad[nMax];
vector<int> G[nMax];

void eulerCycle(int node)
{
    if(G[node].size())
    {
        int fiu=G[node].back();
        G[node].pop_back();
        G[fiu].erase(find(G[fiu].begin(), G[fiu].end(), node));
        eulerCycle(fiu);
    }

    fout<<node<<" ";
}

void dfs(int node, int tata)
{
    viz[node]=1;
    for(vector<int>::iterator it=G[node].begin(); it!=G[node].end(); it++)
    {
        int fiu=*it;
        if(fiu==tata || viz[fiu]==1)
            continue;
        dfs(fiu, node);
    }
}

int main()
{
    int a, b;
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>a>>b;
        G[a].pb(b);
        G[b].pb(a);
        grad[a]++, grad[b]++;
    }

    dfs(1, 0);
    for(int i=1; i<=n; i++)
    {
        if(grad[i] & 1 || viz[i]==0)
        {
            fout<<-1;
            return 0;
        }
    }
    eulerCycle(1);
}