//var I 100p (citirea cu scan) iterativ cu stiva  expl.
#include<cstdio>
#include<vector>
#include<deque>
using namespace std;
int n,m,x,y,i,j,nod,muchieij;
int gr[100003];
bool viz[500003];
vector<int>a[100003];
vector<int>muc[100001];
deque<int>st;
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);
        a[x].push_back(y);
        a[y].push_back(x);
        muc[x].push_back(i);
        muc[y].push_back(i);
        gr[x]++;
        gr[y]++;
    }
    for(i=1;i<=n;i++)
      if(gr[i]%2==1)
      {printf("-1"); return 0; }
    st.push_back(1);
    while(!st.empty())
    {
        i=st.back();
        if(gr[i]==0)
           {    printf("%d ",i); st.pop_back(); }
        else
        {
            j=a[i].back();
            muchieij=muc[i].back();
            a[i].pop_back();
            muc[i].pop_back();
            if(viz[muchieij]==0)
            {
                viz[muchieij]=1;
                st.push_back(j);
                gr[i]--;
                gr[j]--;
            }
        }
    }
    return 0;
}