#include<fstream>
#include<algorithm>
#include<vector>
#include<stack>
#define Nmax 100009
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n,m,x,y;
vector <int> G[Nmax], Cycle;
stack <int> st;

inline int IsEulerian()
{
    for(int i=1;i<=n;++i)
        if(G[i].size() &1) return 0;
    return 1;
}

inline void GetCycle(int S)
{
    for(st.push(S); !st.empty();)
    {
        int node=st.top();
        if(G[node].size())
        {
            int last=G[node].back();
            st.push(last);
            G[node].pop_back();
            G[last].erase(find(G[last].begin(),G[last].end(),node));
        }
        else st.pop() , Cycle.push_back(node);
    }
}

int main()
{
    f>>n>>m;
    for(int i=1;i<=m;++i){
        f>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    if(IsEulerian()){
        GetCycle(1);
        vector<int> :: iterator it;
        for(it=Cycle.begin();it!=Cycle.end();++it)
            g<<*it<<' ';
        g<<'\n';
    }
    else g<<-1<<'\n';
    f.close();g.close();
    return 0;
}