#include <fstream>
#include <vector>
#define MAXN 100100
#define MAXM MAXN*5
#define IN "ciclueuler.in"
#define OUT "ciclueuler.out"
using namespace std;

ifstream fin(IN);
ofstream fout(OUT);

int n,m;
int grad[MAXN];
bool vis[MAXM];
int x[MAXM],y[MAXM];
vector<int> g[MAXN];


void euler(const int &nod)
{
int i
    int cate=g[nod].size();
    while (cate)
    {
        i=g[nod][--cate];
        g[nod].pop_back();
        if (!vis[i])
        {
            vis[i] = true;
            euler(x[i] + y[i] - nod);
        }
    }
    fout<<nod<<' ';
}

int main()
{
    int i
    fin>>n>>m;
    for (i=1; i<=m; ++i)
    {
        fin>>x[i]>>y[i];
        g[x[i]].push_back(i);
        g[y[i]].push_back(i);
        ++grad[x[i]];
        ++grad[y[i]];

    }
    fin.close();

    for (i=1;i<=n;++i)
        if (grad[i]&1)
        {
            fout<<"-1\n";
            fout.close();
            return 0;
        }
    euler(1);
    fout.close();

}