#include<cstdio>
#include<vector>
using namespace std;
int n,i,j,m,nrv[100001],cate,vec[500001],q[500001],pp;
vector<int> v[100001],vc[100001];
void dfs(int nod)
    {
    if(cate<m)
        vec[++cate]=nod;
    else
        pp=1;
    if(cate==m)
        pp=1;
    if(pp==0)
        {
        int i;
        for(i=0;i<v[nod].size();i++)
            if(q[vc[nod][i]]==0&&nrv[v[nod][i]]!=1)
                {

                q[vc[nod][i]]=1;
                nrv[v[nod][i]]--;
                nrv[nod]--;
                dfs(v[nod][i]);
                if(pp==0){
                q[vc[nod][i]]=0;
                nrv[v[nod][i]]++;
                nrv[nod]++;
                cate--;}
                }
        }
    }
int main ()
{
freopen("ciclueuler.in","r",stdin);
freopen("ciclueuler.out","w",stdout);
scanf("%d%d",&n,&m);
int x,y,poz,maxim=0;
for(i=1;i<=m;i++)
    {
    scanf("%d%d",&x,&y);
    v[x].push_back(y);
    vc[x].push_back(i);
    v[y].push_back(x);
    vc[y].push_back(i);
    nrv[x]++;
    nrv[y]++;
    }
for(i=1;i<=n;i++)
    {
    if(nrv[i]%2==1)
        pp=1;
    if(nrv[i]>maxim)
        {
        maxim=nrv[i];
        poz=i;
        }
    }
dfs(poz);
if(cate!=m)
    printf("-1");
else
    for(i=1;i<=cate;i++)
        printf("%d ",vec[i]);
return 0;
}