#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

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

const int maxn = 1e5 + 5;
const int maxm = 5e5 + 5;
vector <int> G[maxn], Ans;
bitset <maxm> Vis;
int n, m, i, X[maxm], Y[maxm];

void Dfs(int node) {
    vector <int> :: iterator it;
    for (it = G[node].begin(); it != G[node].end(); it++) {
        if (Vis[*it] == 0) {
            Vis[*it] = 1;
            Dfs(X[*it] + Y[*it] - node);
        }
    }
    Ans.push_back(node);
}

int main() {
    ios_base :: sync_with_stdio (false);
    vector <int> :: iterator it;
    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);
    }
    for (i = 1; i <= n; i++) {
        if (G[i].size() & 1) {
            fout << "-1\n";
            return 0;
        }
    }
    Dfs(1);
    for (it = Ans.end() - 1; it != Ans.begin(); it--) {
        fout << *it << " ";
    }
    fin.close();
    fout.close();
    return 0;
}