#include <iostream>
#include <fstream>
#include <unordered_map>
#include <stack>

using namespace std;

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

unordered_map<int, int> vec[100003];
int intr[100003];
stack<int> rez;

void eul(int nod) {

    int crr;

    for(unordered_map<int, int>::iterator it = vec[nod].begin(); it != vec[nod].end(); it++) {

        if(it->second == 0)
            continue;

        crr = it->first;
        vec[nod][crr]--;
        vec[crr][nod]--;
        //cout << nod << " " << crr << '\n';
        eul(crr);

    }

    rez.push(nod);

}

int main() {

    int n,m;
    in >> n >> m;
    int x,y;

    for(int i = 1; i <= m; i++) {

        in >> x >> y;

        vec[x][y]++;
        vec[y][x]++;
        intr[x]++;
        intr[y]++;

    }

    for(int i = 1; i <= n; i++) {
        if(intr[i]%2 == 1) {
            out << -1;
            return 0;
        }
    }

    eul(1);

    while(!rez.empty()) {
        out << rez.top() << " ";
        rez.pop();
    }

    return 0;
}