#include <bits/stdc++.h>
using namespace std;
const int NMAX = 1e5;
const int MMAX = 5e5;

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

struct muchie{
  int nod, ind;
};
vector <muchie> edges[NMAX+1];
stack <int> cycle;
stack <int> finalCycle;
int viz[MMAX];
int main() {
  int n, m, i, a, b, node;
  fin >> n >> m;
  for( i = 0; i < m; i++ ) {
    fin >> a >> b;
    edges[a].push_back( { b, i } );
    edges[b].push_back( { a, i } );
  }
  node = 1;
  while( node <= n && edges[node].size() % 2 == 0 )
    node++;
  if( node == n + 1 ) {
    cycle.push( 1 );
    while( cycle.size() ) {
      node = cycle.top();
      if( edges[node].size() ) {
        muchie edge = edges[node].back();
        edges[node].pop_back();
        if( !viz[edge.ind] ) {
          viz[edge.ind] = true;
          cycle.push( edge.nod );
        }
      }
      else {
        finalCycle.push( node );
        cycle.pop();
      }
    }
    while( finalCycle.size() > 1 ) {
      fout << finalCycle.top() << " ";
      finalCycle.pop();
    }
  }
  else
    cout << -1;
  return 0;
}