#include <bits/stdc++.h>


using namespace std;

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

int n, m, x, y;
const int M = 5e5 + 5;
int sel[M];

struct edge
{
    int x, y, ind;
};

vector <edge> G[M];
vector <int> Q;

void Euler(int node)
{
    while(G[node].size()){
        edge K = G[node].back();
        G[node].pop_back();
        if(sel[K.ind] == 0)
        {
            sel[K.ind] = 1;
            Euler(K.y);
        }
    }
    Q.push_back(node);
}
int main()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++) {
        fin >> x >> y;
        G[x].push_back({x, y, i});
        G[y].push_back({y, x, i});
    }
    for(int i = 1; i <= n; i++){
        if(G[i].size() % 2 == 1)
        {
            fout << -1;
            return 0;
        }
    }

    Euler(1);

    Q.pop_back();

    for(auto x: Q) fout << x << ' ';

    return 0;
}