#include<stdio.h>
#include<vector>
using namespace std;
const int  N=100001;
int n,m,nr;
int ce[N];
vector<int> a[N];
vector<pair<int,int> > muchii;
vector<bool> marcat;
 
void citire()
{
    int x,y,i;
    scanf("%d%d",&n,&m);
   for(i=0;i<m;i++)
    {
        scanf("%d%d",&x,&y);
        muchii.push_back(make_pair(x,y));
        marcat.push_back(false);
        a[x].push_back(i);
        a[y].push_back(i);
    }
}
inline int nod(int nrm,int x)
{
    if (muchii[nrm].first==x)
        return muchii[nrm].second;
    return muchii[nrm].first;
}
void euler(int x)
{
    int y,i,nrm;
    for(i=0;i<a[x].size();i++)
   {
        nrm=a[x][i];
       if (marcat[nrm])
            continue;
        marcat[nrm] = true;
        y=nod(nrm,x);
        euler(y);
    }
    ce[++nr]=x;
}
 
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
     
    for (int i=1;i<=n;i++)
        if (a[i].size()%2)
        {
            printf("-1\n");
            return 0;
        }
     
    euler(1);
    if(nr!=m+1 || ce[1]!=1)
    {
        printf("-1\n");
        return 0;
    }
    for (int i=nr;i>1;i--)
        printf("%d ",ce[i]);
     
    return 0;
}