#include <algorithm>
#include <fstream>
#include <vector>
#define N 100002
#define M 500002

using namespace std;

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

int n,m;
int from[M], to[M];
bool usedEdge[M];

vector<int>A[N];
vector<int>noduri;
vector<int>Stack;

int main()
{
    int a,b;
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>a>>b;
        A[a].push_back(i);
        A[b].push_back(i);
        from[i]=a;
        to[i]=b;
    }
    for(int i=1; i<=n; i++)
    {
        if(A[i].size()%2)
        {
            fout<<"-1\n";
            return 0;
        }
    }
    Stack.push_back(1);
    while(!Stack.empty())
    {
        int nod=Stack.back();
        if(!A[nod].empty())
        {
            int e=A[nod].back();
            A[nod].pop_back();
            if(!usedEdge[e])
            {
                usedEdge[e]=true;
                int t;
                if(from[e]==nod)
                {
                    t=to[e];
                }
                else
                {
                    t=from[e];
                }
                Stack.push_back(t);

            }
        }
        else
        {
            Stack.pop_back();
            noduri.push_back(nod);
        }
    }
    for(int i=noduri.size()-1; i; i--)
    {
        fout<<noduri[i]<<' ';
    }
    return 0;
}