#include <fstream>
#include <bitset>
#include <vector>
using namespace std;
ifstream fi("ciclueuler.in");
ofstream fo("ciclueuler.out");
const int Dim = 100003;

vector<int> G[5*Dim],d;
bitset<5*Dim> viz;
struct muchie{int x,y;} E[5*Dim];
int n,m;

void ReadGraph()
{  int x,y;
    fi>>n>>m;
    for(int i =1;i<=m;i++)
    {   fi>>x>>y;
        G[x].push_back(i);
        G[y].push_back(i);
        E[i].x=x;
        E[i].y=y;
    }
}

int Verif_eulerian()
{
    for(int i=1;i<=n;i++)
            if(G[i].size()% 2 == 1)  return 0;
    return 1;
}

inline void DF(int nod)
{
    for(auto & p : G[nod])
        if(viz[p]==0)
            {
                viz[p]=1;
                DF(E[p].x + E[p].y - nod);
             }
             d.push_back(nod);
}
int main()
{
    ReadGraph();
    if (Verif_eulerian()==0) {fo<<"-1";return 0;}
       else {DF(1);
            for(int i=0;i<d.size();i++)
                 fo<<d[i]<<" ";
            }

    return 0;
}