#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;
int n,m,i,x,y,k,nr,st[500005],e[500005],start;
bool eulerian, viz[500005];

vector < pair <int, int> > v[100005];


int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for (i=1; i<=m; i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back( make_pair(y,i));
        v[y].push_back(make_pair(x,i));
        viz[i]=1;
        start=x;
    }
    eulerian=true;
    for (i=1; i<=n&&eulerian==true; i++)
        if (v[i].size()%2==1)
        eulerian=false;
    if (eulerian==false)
    {
        printf("-1\n");
        return 0;
    }
    k=1;st[k]=start;
    while(k>0){
        if(v[st[k]].size()>0){

           while(v[st[k]].size()>0&&viz[v[st[k]].back().second]==0){
             v[st[k]].pop_back();

           }
           if(v[st[k]].size()>0){
           int nod=v[st[k]].back().first;
           int mc=v[st[k]].back().second;
            viz[mc]=0;
             v[st[k]].pop_back();
            k++;
            st[k]=nod;
           }
        }
        else{
            e[++nr]=st[k--];

        }


    }

    if(nr-1!=m){
          printf("-1\n");
        return 0;

    }

    for (i=1; i<nr; i++)
        printf("%d ",e[i]);
    printf("\n");
    return 0;
}