#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define nmax 100005

using namespace std;

int n, m;
int grad[nmax];
vector <int> G[nmax];
stack <int> sol;

bool gradImpar() {
    for (int i = 1; i <= n; i++)
        if (grad[i] % 2 == 1)
            return 1;
    return 0;
}

void sterge(int nod, int vc) {
    for (vector <int> ::iterator it = G[nod].begin(); it != G[nod].end(); ++it)
        if (*it == vc) {
            G[nod].erase(it);
            break;
        }
}

void euler(int nod) {
    stack <int> s;
    s.push(nod);
    for (; s.size();) {
        nod = s.top();
        if (G[nod].size()) {
            int vecinCurent = G[nod][0];
            G[nod].erase(G[nod].begin());
            sterge(vecinCurent, nod);
            s.push(vecinCurent);
        } else {
            sol.push(s.top());
            s.pop();
        }
    }
}

int main() {
    
    ifstream fin("ciclueuler.in");
    ofstream fout("ciclueuler.out");
    
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
    
    if (gradImpar()) {
        fout << -1 << "\n";
        return 0;
    }
    
    euler(1);
    
    for (; sol.size() > 1;) {
        fout << sol.top() << " ";
        sol.pop();
    }
    
    fin.close();
    fout.close();
    
    return 0;
}