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

using namespace std;

struct vecin
{
    int nod,ind;
};

int mark[500005],st[500005];

vector <vecin> v[100005];

vector<int> rez;

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    int n,m,i,varf,ok,x,y;
    vecin a;
    cin>>n>>m;
    for(i=1;i<=m;i++)
    {
        cin>>x>>y;
        a.nod=y;
        a.ind=i;
        v[x].push_back(a);
        a.nod=x;
        v[y].push_back(a);
    }
    for(i=1;i<=n;i++)
        if(v[i].size()%2==1)
        {
            cout<<"-1";
            return 0;
        }
    int top=1;
    st[top]=1;
    while(top>0)
    {
        varf=st[top];
        ok=0;
        for(vector <vecin>:: iterator it=v[varf].begin();it!=v[varf].end() && !ok;it++)
        {
            a=*it;
            if(!mark[a.ind])
            {
                    st[++top]=a.nod;
                    mark[a.ind]=1;
                    ok=1;
            }
        }
        if(ok==0){
          rez.push_back(st[top]);
          top--;
        }
    }
    if(rez.size()!=m+1)
    {
        cout<<"-1";
        return 0;
    }
    for(vector <int>::iterator it=rez.begin()+1;it!=rez.end();it++)
        cout<<(*it)<<' ';
    return 0;
}