#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

struct custom_hash_pair {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(pair<uint64_t,uint64_t> x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x.first + FIXED_RANDOM)^(splitmix64(x.second + FIXED_RANDOM) >> 1);
    }
};

#define all(x) (x).begin(), (x).end()
#define allg(x) (x).begin(), (x).end(), greater<int>()
using ull = unsigned long long;
using ll =  long long;
using ld = double;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<ld>;
using si = set<int>;
using ssi = set<si>;
using sl = set<ll>;
using ssl = set<sl>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvl = vector<vl>;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vs = vector<string>;
using vpi = vector<pii>;
using vpl = vector<pll>;
using vvpl = vector<vpl>;
#define umap unordered_map
#define eb emplace_back
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define mp make_pair
#define ff first
#define ss second
#define ar array
inline void yn(bool b)
{
    if(b==true)
        cout<<"Yes\n";
    else
        cout<<"No\n";
}
  inline void fastio() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
}

ll Mod = 1e9+7;
inline bool hasbit(ll nr, ll pos)
{
    return (nr&(1ll<<pos));
}

const string TASK("ciclueuler");
ifstream fin(TASK + ".in");
ofstream fout(TASK + ".out");
#define cin fin
#define cout fout
const ll Inf = 0x3f3f3f3f;
bool testCase = false;
const ll Nmax=1e5+10;

ll n,m;
vl sir;
vvpl G(Nmax);
bool viz[Nmax];
vl stk;

void solve_testcase()
{
  cin>>n>>m;
  for(int i=1;i<=m;i++)
  {
    ll x,y;
    cin>>x>>y;
    G[x].eb(y,i);
    G[y].eb(x,i);
  }
  for(int i=1;i<=n;i++)
    if((int)G[i].size()%2!=0)
  {
    cout<<-1<<'\n';
    return;
  }
  stk.eb(1);
  while(!stk.empty())
  {
  int nod = stk.back();
  if(!G[nod].empty())
  {
    pll c = G[nod].back();
    G[nod].pop_back();
    if(!viz[c.ss])
    {
      viz[c.ss] = true;
      stk.eb(c.ff);
    }
  }
  else{
  stk.pop_back();
  sir.eb(nod);
  }
  }
  sir.pop_back();
  for(auto c:sir)
    cout<<c<<" ";
}

void pregenerate()
{

}

/// Check for interruption of input!!
/// a+b=a^b+2*(a&b)
int main() {
    fastio();
    pregenerate();
    ll t=1;
    if (testCase) cin >> t;
    while (t--)
    {   //cout<<t<<endl;
        solve_testcase();
    }
    return 0;
}