#include <cstdio>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

const int NMAX = 100005;
int n,m;
vector<int>G[NMAX];
stack<int>st;
vector<int>sol;
bool viz[NMAX];

inline void sterge(int nod,int l)
{
  vector<int>::iterator it;
  it = find(G[l].begin(),G[l].end(),nod);
  G[l].erase(it);
}

void euler(int nod)
{
    int node,other;
    node = nod;
    while(G[node].size()>0)
    {
        st.push(node);
        other = G[node][G[node].size()-1];
        G[node].pop_back();
        sterge(node,other); /// sterge nod de pe linia other
        node = other;
    }
}

void dfs(int nod)
{
  viz[nod] = 1;
  for(int i = 0 ; i < G[nod].size() ; i++)
  {
    int val = G[nod][i];
    if(!viz[val])
      dfs(val);
  }
}

bool verifGrade()
{
  for(int i = 1 ; i <= n ; i++)
  {
    if(G[i].size() % 2 == 1)
      return false;
  }
  return true;
}

bool verifOK()
{
  int ct = 0;
  for(int i = 1 ; i <= n ; i++)
      if(!viz[i])
      {
        dfs(i);
        ct++;
      }
  if(ct >= 2)
    return false;
  if(verifGrade() == false)
    return false;
  return true;
}

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    int a , b;
    scanf("%d%d",&n,&m);
    for(int i = 1 ; i <= m ; i++)
    {
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
        G[b].push_back(a);
    }
    if(verifOK())
    {
      sol.push_back(1);
      euler(1);
      while(!st.empty())
      {
        int nod = st.top();
        sol.push_back(nod);
        if(G[nod].size()!=0)
          euler(nod);
        st.pop();
      }
      for(int i = 0 ; i < sol.size()-1 ; i++)
        printf("%d ",sol[i]);
    }
    else
      printf("-1");
    return 0;
}