#include <bits/stdc++.h>
#define DMAX 100005
#define NMAX 500005

using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
list<int> LA[DMAX];
int n;
//bool uz1[DMAX];
//bool uzm[NMAX];
//int g[DMAX];
void citire();
bool verif();
void DFS1(int x);
int main()
{
    citire();
    if(verif())
       {DFS1(1);fout<<'\n';}
       else
       fout<<"-1"<<'\n';
    return 0;
}
void citire()
{int a,b,M,i;
    fin>>n;
    fin>>M;
    for(i=1;i<=M;i++)
         {
          fin>>a>>b;
          LA[a].push_back(b);
          //if(a!=b)
            {
             LA[b].push_back(a);
            }
          //g[a]++;
          //g[b]++;
         }
}
bool verif()
{int i;
   //DFS(1);
   for(i=1;i<=n;i++)
       {//if(uz1[i]==0)
           //return 0;
        if(LA[i].size()%2)
           return 0;
       }
   return 1;
}
/*void DFS(int x)
{int i;
 uz1[x]=1;
    for(i=0;i<LA[x].size();i++)
        if(!uz1[LA[x][i].v])
           DFS(LA[x][i].v);
}*/
void DFS1(int x)
{int nod;
 //list <int>::iterator nod1;
    while(LA[x].size())
        {nod=LA[x].front();
         LA[x].pop_front();
         //if(g[nod]>0)
           {
            LA[nod].erase(find(LA[nod].begin(),LA[nod].end(),x));
            //g[nod]--;
            DFS1(nod);
           }
        }
    fout<<x<<' ';
}