#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
#include <bitset>
#define INF 0x3f3f3f3f
#define q g[nod][g[nod].size() - 1]
using namespace std;

ifstream is("ciclueuler.in");
ofstream os("ciclueuler.out");

using VI = vector<int>;
using VVI = vector<VI>;
using VP = vector<pair<int, int>>;
using VPP = vector<pair<int, pair<int, int>>>;

int n, m;
VI a;
VP e;
VVI g;
bitset<500001> ok;

void Read();
inline void Solve(int nod, int k);
bool Check();

int main()
{
    Read();
    if ( !Check() )
        os << "-1";
    else
        Solve(1, 0);
    is.close();
    os.close();
    return 0;
}

inline void Solve(int nod, int k)
{
    while ( g[nod].size() )
        if ( ok[q] )
            g[nod].pop_back();
        else
        {
            ok[q] = 1;
            Solve(e[q].first + e[q].second - nod, k + 1);
        }
    if ( a.size() )
    {
        os << a[0] << " ";
        a.pop_back();
    }
    a.push_back(nod);
}

bool Check()
{
    if ( m < n - 1 )
        return false;
    for ( size_t x = 1; x <= n; ++x )
        if ( !g[x].size() || g[x].size() & 1 )
            return false;
    return true;
}

void Read()
{
    is >> n >> m;
    g = VVI(n + 1);
    e.push_back(make_pair(0, 0));
    int x, y;
    for ( int i = 1; i <= m; ++i )
    {
        is >> x >> y;
        g[x].push_back(i);
        g[y].push_back(i);
        e.push_back(make_pair(x, y));
    }
}