#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n, m, grad[100010];
struct muchie{
    int x, y;
    int viz;
}muchii[500010];
int viz[100010];
vector<int>graf[100010];
stack<int>a;
void citire()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int a, b;
        f>>a>>b;
        graf[a].push_back(i);
        graf[b].push_back(i);
        grad[a]++;
        grad[b]++;
        muchii[i].x=a;
        muchii[i].y=b;
        muchii[i].viz=0;
    }
}

void dfs(int x)
{
    viz[x]=1;
    for(auto &v:graf[x])
        if(viz[v]==0)
            dfs(v);
}

int verificare()
{
    for(int i=1; i<=n; i++)
    {
        if(grad[i]==0)
            viz[i]=1;
        if(grad[i]%2!=0)
            return 0;
    }/**
    int nr=0;
    for(int i=1; i<=n; i++)
        if(viz[i]==0)
        {
            nr++;
            dfs(i);
        }
    if(nr!=1)
        return 0;*/
    return 1;
}

void ciclu()
{
    a.push(1);
    while(!a.empty())
    {
        int x=a.top();
        if(graf[x].empty())
        {
            a.pop();
            if(!a.empty())
                g<<x<<' ';
            continue;
        }
        int y=graf[x].back();
        graf[x].pop_back();
        if(muchii[y].viz)
            continue;
        muchii[y].viz=1;
        if(x==muchii[y].x)
            a.push(muchii[y].y);
        else
            a.push(muchii[y].x);
    }
}
int main()
{
    citire();
    if(verificare()==0)
        g<<-1;
    else
        ciclu();
    return 0;
}