#include <fstream>
#include <vector>

using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int nmax= 100000;
const int mmax= 500000;

int n, m;

bool u[mmax+1];
int a[mmax+1], b[mmax+1];

vector <int> g[nmax+1], s;

int main(  ) {
    fin>>n>>m;
    for ( int i= 1, x, y; i<=m; ++i ) {
        fin>>x>>y;

        g[x].push_back(i);
        g[y].push_back(i);

        a[i]= x, b[i]= y;
    }

    for ( int i= 1; i<=n; ++i ) {
        if ( (int)g[i].size()%2==1 ) {
            fout<<"-1\n";
            return 0;
        }
    }

    for ( s.push_back(1); !s.empty(); ) {
        int x= s.back();
        if ( (int)g[x].size()>0 ) {
            int y= g[x].back();
            g[x].pop_back();

            if ( u[y]==0 ) {
                u[y]= 1;
                if ( b[y]==x ) {
                    s.push_back(a[y]);
                } else {
                    s.push_back(b[y]);
                }
            }
        } else {
            s.pop_back();
            if ( (int)s.size()>0 ) {
                fout<<x<<" ";
            }
        }
    }
    fout<<"\n";

    return 0;
}