#include <bits/stdc++.h>
using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int sum[500003];
vector<int> g[100003];
int nr[100003];
vector<int> sol;

void solve(int nod){
  while(!g[nod].empty()){
    sum[g[nod].back()]-=nod;
    int x=sum[g[nod].back()];
    g[nod].pop_back();
    if(x){
      solve(x);
    }
  }
  sol.push_back(nod);
}

int main()
{
  int n, m;
  fin>>n>>m;
  for(int i=1;i<=m;++i){
    int a, b;
    fin>>a>>b;
    sum[i]=a+b;
    g[a].push_back(i);
    g[b].push_back(i);
    nr[a]++;
    nr[b]++;
  }
  for(int i=1;i<=n;++i){
    if(nr[i]&1){
      fout<<-1<<"\n";
      return 0;
    }
  }
  solve(1);
  for(int i=0;i<sol.size()-1;++i){
    fout<<sol[i]<<" ";
  }
  fout<<"\n";
  return 0;
}