#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

const int NMAX = 100007;
const int MMAX = 500007;

ifstream cin("ciclueuler.in");
ofstream cout("ciclueuler.out");

vector < int > sol;
int poz[NMAX], ap[NMAX], viz[NMAX];
pair < int, int > edges[MMAX];
vector < int > v[NMAX];
int n, m;

void euler(int node) {
    while(poz[node] < v[node].size()) {
        if(viz[v[node][poz[node]]] == 1) {
            ++poz[node];
        }
        else {
            int w = v[node][poz[node]];
            int vecin =  edges[w].first + edges[w].second - node;
            ++poz[node];
            viz[w] = 1;
            euler(vecin);
        }
    }
    sol.push_back(node);
}

int main() {
    cin >> n >> m;
    for(int i = 1; i <= m; ++i) {
        int a, b;
        cin >> a >> b;
        edges[i] = make_pair(a, b);
        v[a].push_back(i);
        v[b].push_back(i);
        ++ap[a];
        ++ap[b];
    }
    for(int i = 1; i <= n; ++i) {
        if(ap[i] % 2 == 1) {
            cout << -1;
            return 0;
        }
    }
    euler(1);
    for(int i = sol.size() - 1; i >= 1; --i) {
        cout << sol[i] << " ";
    }
    return 0;
}