#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;
};
bool viz[MMAX];
vector <muchie> edges[NMAX+1];
vector <int> cycle;

void dfs( int node ) {
  int i;
  for( i = 0; i < edges[node].size(); i++ ) {
    if( !viz[edges[node][i].ind] ) {
      viz[edges[node][i].ind] = 1;
      dfs( edges[node][i].nod );
    }
  }
  cycle.push_back( node );
}
int main() {
  int n, m, i, a, b;
  fin >> n >> m;
  for( i = 0; i < m; i++ ) {
    fin >> a >> b;
    edges[a].push_back( { b, i } );
    edges[b].push_back( { a, i } );
  }
  dfs( 1 );
  i = 0;
  while( i < m && viz[i] )
    i++;
  if( i == m ) {
    while( cycle.size() > 1 ) {
      fout << cycle.back() << " ";
      cycle.pop_back();
    }
  }
  else
    fout << -1;
  return 0;
}