#include<fstream>
#include<vector>
#include<stack>
#include<set>
std::ifstream fin("ciclueuler.in");
std::ofstream fout("ciclueuler.out");
const int NMAX=100005;
std::multiset<int>G[NMAX];
std::vector<int>degree(NMAX);
int n, m;
void read()
{
    fin>>n>>m;
    for(int i=0; i<m; ++i)
    {
        int from, to;
        fin>>from>>to;
        G[from].insert(to);
        G[to].insert(from);
        ++degree[from];
        ++degree[to];
    }

}
bool eulerian()
{
    for(int i=1; i<=n; ++i)
        if(degree[i]%2)
            return false;
    return true;
}
void get_cycle()
{
    std::stack<int>curr_path;
    std::vector<int>sol;
    int v=1;
    curr_path.push(1);
    while(!curr_path.empty())
    {
        if(!G[v].empty())
        {
            int nxt=*G[v].begin();
            G[v].erase(G[v].begin());
            //if(nxt!=v)
            //{
                auto it=G[nxt].find(v);
                G[nxt].erase(it);
           // }
            curr_path.push(v);
            v=nxt;
        }
        else
        {
            sol.push_back(v);
            v=curr_path.top();
            curr_path.pop();
        }
    }
    for(int i=0; i<sol.size()-1; ++i)
        fout<<sol[i]<<' ';
}
int main()
{
    read();
    if(eulerian())
        get_cycle();
    else
        fout<<"-1";
    return 0;
}