#include <fstream>
#include <stack>
#include <queue>
#include <algorithm>
#include <vector>
#define NMAX 100005

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

vector<int> G[NMAX];
stack<int> stiv;
queue<int> Q;
int N,M;
int viz[NMAX];

void BFS(int vf)
{
    Q.push(vf); viz[vf] = 1;
    int i;
    while( !Q.empty() )
    {
        vf = Q.front();
        Q.pop();
        for(i = 0; i < G[vf].size(); i++)
            if( viz[ G[vf][i] ] == 0 )
                {
                    Q.push( G[vf][i] );
                    viz[ G[vf][i] ] = 1;
                }
    }
}

bool VerificaEulerian()
{
    BFS(1);
    for(int i = 1;i<=N;i++)
        if(!viz[i] || G[i].size() %2 == 1)
            return false;

    return true;

}

int main()
{
    int x,y;
    fin>>N>>M;
    for(int i = 1;i<=M;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }

    if(VerificaEulerian())
    {
        int vf = 1,vf2;
        stiv.push(vf);

        while(!stiv.empty())
        {
            vf = stiv.top();
            if(G[vf].size() == 0)
            {
                fout<<vf<<" ", stiv.pop();
            }
            else
            {
                vf2 = G[vf][G[vf].size()-1];
                stiv.push(vf2);
                G[vf].pop_back();
                G[vf2].erase(find(G[vf2].begin(),G[vf2].end(), vf));
            }
        }

    }

    else fout<<"-1"<<'\n';
    return 0;
}