#include <bits/stdc++.h>
using namespace std;
#define cin fin
#define cout fout
ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");

int v[100005];
vector<vector<int>>vec;
pair<int,int>edges[500005];
bool used[500005];
int n,m;
int rez[500005];
int rez2=0;
void Dfs(int nd)
{
    while(!vec[nd].empty())
    {
        int r=vec[nd].back();
        vec[nd].pop_back();
        if(used[r]==false)
        {
            used[r]=true;
            if(edges[r].first==nd)
                Dfs(edges[r].second);
            else
                Dfs(edges[r].first);
        }
    }
    rez[rez2]=nd;
    rez2++;
}

int main()
{
    cin>>n>>m;
    vec.resize(n+1);
    for(int i=0;i<m;i++)
    {
        int a,b;
        cin>>a>>b;
        v[a]++;
        v[b]++;
        edges[i].first=a;
        edges[i].second=b;
        vec[a].push_back(i);
        vec[b].push_back(i);
    }
    int cnt=0;
    for(int i=1;i<=n;i++)
    {
        if(v[i]%2==1)
        {
            cnt++;
        }
    }
    if(cnt>1)
        cout<<-1;
    else
    {
        Dfs(1);
        for(int i=rez2-1;i>=1;i--)
            cout<<rez[i]<<" ";
    }

    return 0;
}