# include <fstream>
# include <vector>
# include <stack>
# define DIM 100010
# define f first
# define s second
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
vector<pair<int,int> > Lista[DIM];
stack<int> st;
int sol[5*DIM],f[5*DIM],Marcat[DIM],d[DIM],n,m,x,y,i,k,nc,nv;
void euler(int nc){
    Marcat[nc]=1;
    for(int i=0;i<Lista[nc].size();i++){
        int nv=Lista[nc][i].f;
        if(Marcat[nv]==0)
            euler(nv);
    }
}
int main () {
    fin>>n>>m;
    for(i=1;i<=m;i++){
        fin>>x>>y;
        Lista[x].push_back(make_pair(y,i));
        Lista[y].push_back(make_pair(x,i));
        d[x]++;
        d[y]++;
    }
    euler(1);
    for(i=1;i<=n;i++)
        if(Marcat[i]==0||(d[i]%2==1)){
            fout<<"-1\n";
            return 0;
        }
    st.push(1);
    while(!st.empty()){
        nc=st.top();
        if(d[nc]==0){
            sol[++k]=nc;
            st.pop();
            continue;
        }
        i=Lista[nc].size()-1;
        while(f[Lista[nc][i].s]){
            Lista[nc].pop_back();
            i--;
        }
        f[Lista[nc][i].s]=1;
        nv=Lista[nc][i].f;
        st.push(nv);
        d[nc]--;
        d[nv]--;
    }
    for(i=1;i<k;i++)
        fout<<sol[i]<<" ";
    return 0;
}