#include <fstream>
#include <vector>
#define NMAX 100100
#define MMAX 500100
using namespace std;

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

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

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


int main()
{
    int i,j;
    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]];
    }
    for (j=1;j<= n;++j)
        if (grad[j] & 1) {
            fout << "-1\n";

            return 0;
        }

    euler(1);
    fout.close();
    fin.close();
}