#include<fstream>
#include<vector>
#include<deque>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n,m,x,y,i,nod,x1,x2;
int in[100005];
vector<int>v[100005],muc[100005];
deque<int>stiva,sol;
bool viz[500005];
int main()
{
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
        muc[x].push_back(i);
        muc[y].push_back(i);
        in[x]++;
        in[y]++;
    }
    for(i=1;i<=n;i++)
      if((in[i]&1)==1)//in[i]%2
      {
          g<<-1;
          return 0;
      }
    stiva.push_back(1);
    while(!stiva.empty())
    {
        nod=stiva.back();
        if(in[nod]==0)
        {
            stiva.pop_back();
            g<<nod<<" ";
        }
        else
        {
            x1=v[nod].back();
            x2=muc[nod].back();
            v[nod].pop_back();
            muc[nod].pop_back();
            if(viz[x2]==0)
            {
                viz[x2]=1;
                in[x1]--;
                in[nod]--;
                stiva.push_back(x1);
            }
        }
    }
    return 0;
}