#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream is ("ciclueuler.in");
ofstream os ("ciclueuler.out");

vector <int> ::iterator it;
vector <int > V[100010], g, v, answ;
queue <int> Q;
vector <bool> viz;
int N, M;

void Read();
void BFS();
void Solve(int x);
bool Ok();
void Erase(int x, int y);

int main()
{
    Read();
    BFS();
    if(!Ok) os << -1;
    else
    {
        int nod = 1;
        do {
            Solve( nod );
            nod = v[v.size()-1];
            v.pop_back();
            answ.push_back( nod );
        } while( !v.empty() );

        for(it = answ.begin(); it != answ.end(); ++it)
            os << *it << " ";
    }
    is.close();
    os.close();
    return 0;
}
void Read()
{
    int x, y;
    is >> N >> M;
    viz.resize(N+1, false);
    g.resize(N+1);
    for(int i = 1; i <= M; ++i)
    {
        is >> x >> y;
        V[x].push_back(y);
        V[y].push_back(x);
        g[x]++, g[y]++;
    }
}
void BFS()
{
    int nod;
    Q.push(1);
    viz[1] = true;
    while(!Q.empty())
    {
        nod = Q.front();
        Q.pop();
        for(it = V[nod].begin(); it != V[nod].end(); ++it)
            if(!viz[*it])
            {
                viz[*it] = true;
                Q.push(*it);
            }
    }
}
bool Ok()
{
    for(int i = 1; i <= N; ++i)
        if(!viz[i] || g[i]%2)
            return false;
    return true;
}
void Solve(int x)
{
    int y;
    while(true)
    {
        if(!V[x].size())
            break;

        y = V[x][V[x].size()-1];
        v.push_back(x);
        V[x].pop_back();
        Erase(x, y);
        x = y;
    }

}
void Erase(int x, int y)
{
    for(it = V[y].begin(); it != V[y].end(); ++it)
        if(*it == x)
        {
            V[y].erase(it);
            break;
        }
}