#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

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

const int MaxN=100005;
int N,M;
vector<int> G[MaxN];

void Read();
void Euler(int startNode);

int main()
{
    Read();
    for(int i=1;i<=N;++i)
        if(!G[i].size() || G[i].size()%2==1)
    {
        fout<<"-1\n";
        return 0;
    }

    Euler(1);

    fout.close();
    return 0;
}

void Read()
{
    fin>>N>>M;
    for(int i=1;i<=M;++i)
    {
        int x,y;
        fin>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    fin.close();
}
void Euler(int startNode)
{
    stack<int> St;
    vector<int> cycle;
    St.push(startNode);

    while(!St.empty())
    {
        int x=St.top();
        if(G[x].size())
        {
            int newx=G[x].back();
            G[x].pop_back();
            G[newx].erase(find(G[newx].begin(),G[newx].end(),x));
            St.push(newx);
        }
        else
        {
            St.pop();
            if(!St.empty()) cycle.push_back(x);
        }
    }

    for(auto i : cycle)
        fout<<i<<" ";
}