#include <bits/stdc++.h>

using namespace std;
class prs{
private:
    FILE *fin;
    char *buff;
    int sp;
    char read_ch(){
    ++sp;
    if(sp==4096){
        sp=0;
        fread(buff,1,4096,fin);
    }
    return buff[sp];
    }
public:
    prs(const char *name){
    fin=fopen(name,"r");
    buff=new char [4096]();
    sp-4095;
    }
    prs& operator >> (int &n){
    char c;
    while(!isdigit(c=read_ch()));
    n=c-'0';
    while(isdigit(c=read_ch()))
        n=n*10+c-'0';
    return *this;
    }
};
const int nmax=int(1e5);
vector <pair<int,int>> adj[nmax];
vector <int> ans;
int elim[5*nmax+1];
int n,m;
int main()
{
    prs fin("ciclueuler.in");
    freopen("ciclueuler.out","w",stdout);
    fin>>n>>m;
    for(int i=1,x,y;i<=m;++i){
        fin>>x>>y;
        adj[x].push_back({y,i});
        adj[y].push_back({x,i});
    }
    for(int i=1;i<=n;++i)
    if(adj[i].size()%2==1){
        cout<<"-1";
        return 0;
    }
    stack <int> st;
    st.push(1);

    while(!st.empty()){
    int nod=st.top();
    if(adj[nod].size()){
        int x=adj[nod][adj[nod].size()-1].second;
        if(!elim[x]){
            elim[x]=1;
            st.push(adj[nod][adj[nod].size()-1].first);
        }
        adj[nod].pop_back();
    }
    else{
    ans.push_back(nod);
    st.pop();
    }
    }
    for(auto x:ans)
        printf("%d ",x);
}