#include <fstream>
#include <vector>
#include <map>
using namespace std;

ifstream cin( "ciclueuler.in" );
ofstream cout( "ciclueuler.out" );

const int MAX = 100002;

map<pair<int, int>, bool> mp;
vector<int> noduri[ MAX ];
vector<int> rez;
int n, m, x, y;

void make( int nod ) {
    rez.push_back( nod );
    while( noduri[ nod ].size() ) {
        int nn = noduri[ nod ].back();
        noduri[ nod ].pop_back();
        if( mp.count( make_pair( min( nod, nn ), max( nn, nod ) ) ) == 0 ) {
            mp[ make_pair( min( nod, nn ), max( nn, nod ) ) ] = 1;
            make( nn );
        }
    }
}

int main()
{
    cin >> n >> m;
    for( int i = 0; i < m; i++ ) {
        cin >> x >> y;
        noduri[ x ].push_back( y );
        noduri[ y ].push_back( x );
    }

    bool ok = true;
    for( int i = 1; i <= n; i++ )
        if( noduri[ i ].size() & 1 )
            ok = false;

    if( ok == true ) {
        make( 1 );
        for( int i = 0; i < rez.size() - 1; i++ )
            cout << rez[ i ] << ' ';
    } else cout << "-1";
    return 0;
}