#include <cstdio>
# include <vector>
# include <list>
using namespace std;
vector <int> v[100010];
int x,y,i,n,m,nr,nod;
list <int> q;
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d %d\n",&n,&m);
    for (i=1; i<=m; i++)
    {
        scanf("%d %d\n",&x,&y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for (i=1; i<=n; i++)
        if (v[i].size()%2==1)
        {
            printf("%d\n",-1);
            return 0;
        }
    nr=0;
    q.push_front(1);
    while (!q.empty())
    {
        nod=q.front();
        if (v[nod].empty())
        {
            q.pop_front();
            nr++;
            if (nr<=m)
                printf("%d ",nod);
             continue;
        }
        else
        {
            y=v[nod].back();
            q.push_front(y);
            v[nod].pop_back();
            for (vector <int> :: iterator it=v[y].begin(); it!=v[y].end(); ++it)
                if (*it==nod)
                {
                    v[y].erase(it);
                    break;
                }
        }
    }
    printf("\n");
    return 0;
}