#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
int n,m,i,x,y,muchie,nod,v1[500005],v2[500005];
bool viz[500005];
vector <int> A[100005],st,v;
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(i);
        A[y].push_back(i);
        v1[i]=x;
        v2[i]=y;
    }
    for(i=1; i<=n; i++)
    {
        if(A[i].size()%2==1)
            {printf("-1");
            return 0;}
    }
    st.push_back(1);
    while(!st.empty())
    {
        nod=st.back();
        if(!A[nod].empty())
        {
            muchie=A[nod].back();
            A[nod].pop_back();
            if(!viz[muchie])
                {viz[muchie]=true;
                if(v1[muchie]==nod)
                    st.push_back(v2[muchie]);
                    else
                        st.push_back(v1[muchie]);}

        }
        else
        {
            st.pop_back();
            v.push_back(nod);
        }
    }
   for(i=0; i<v.size()-1; i++)
        printf("%d ", v[i]);


    return 0;
}