#include <fstream>
#include <iostream>
#include<stdio.h>
#include <stack>
#include <vector>
#include <algorithm>

using namespace std;
//ifstream fin("ciclueuler.in");
//ofstream fout("ciclueuler.out");
vector<int>G[100005];
vector<int>::iterator it;
stack<int>st;
int n,m,i,j,k,l,r,x,y,s,smax,viz[100005];
bool ok;
void dfs(int x)
{
    int q;
    viz[x]=1;
    for(int v=0;v<G[x].size();v++)
    {
        q=G[x][v];
        if(!viz[q])
        {
            dfs(q);
        }
    }
}
void euler(int node)
{


    while(!G[node].empty())
    {
        st.push(node);
       int other=G[node].back();
       // it=find(G[other].begin(),G[other].end(),node);
        G[other].erase(find(G[other].begin(),G[other].end(),node));
        G[node].pop_back();
        node=other;
    }



}
int main()
{
   // fin>>n>>m;
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d\n",&n,&m);
    for(i=1;i<=m;i++)
    {
        //fin>>x>>y;
        scanf("%d %d\n",&x,&y);
        G[x].push_back(y);
        G[y].push_back(x);

    }
    ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
    for(i=1;i<=n;i++)
        if(G[i].size()%2==1)
        ok=1;
    /*if(!ok)
        {
            dfs(1);
            for(i=1;i<=n;i++)
            if(!viz[i])
                ok=1;
        }*/
    if(!ok)
    {
        //st.push(1);

       // fout<<1<<" " ;
       l=1;
       //fout<<1<<" ";
        printf("1 ");
       do
        {
            euler(l);
            l=st.top();
            //fout<<l<<" ";
             printf("%d ",l);
            st.pop();

        } while(st.size()>1);

    }
    else
        printf("-1\n");
        //fout<<-1;
    // fout<<st.size();

    return 0;
}