#include <iostream>
#include <fstream>
#include <vector>
#include <set>
#include <iterator>
#define NMAX 100003
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

multiset <int> nodes[NMAX];
multiset <int> :: iterator it;
int n, sizeOf[NMAX];
long long m;
vector <int> result;
void read(){
    f >> n >> m;
    int x, y;
    for (int i = 1; i <= m; i++){
        f >> x >> y;
        nodes[x].insert(y);
        sizeOf[x]++;
        sizeOf[y]++;
        if (x != y){
            nodes[y].insert(x);
        }
    }
}
void euler(int node){
    it = nodes[node].begin();
    while (it != nodes[node].end()){
        int next = *it;
    	//Erase the current node
    	nodes[node].erase(nodes[node].find(next));
        if (next !=  node){
            nodes[next].erase(nodes[next].find(node));
        }
    	euler(next);
    	it = nodes[node].begin();
    }
    result.push_back(node);
}
int main()
{
    read();
    for (int i = 1; i <= n; i++) {
        if (sizeOf[i] & 1) {
            g << "-1\n";
            return 0;
        }
    }
    euler(1);
    for (int i = result.size() - 1; i > 0; i--)
        g << result[i] << " ";
    return 0;
}