#include<iostream>
#include<fstream>
#include<cstdio>
#include<vector>
#include<string>
#include<cstring>
#include<queue>
#include<map>
#include<set>
#include<algorithm>
#include<iomanip>
#include<bitset>
using namespace std;

const int N = 100100;

int n, m, a[5 * N], b[5 * N], gr[N];
bool ver[5 * N];
vector<int> v[N], rez;
vector<int>::iterator it[N];

void eul(int nod) {

    for(vector<int>::iterator it = v[nod].begin(); it != v[nod].end(); ++it) if(!ver[*it]) {
        int oth = a[*it] + b[*it] - nod;
        ver[*it] = 1;

        eul(oth);
    }

    rez.push_back(nod);
}

int main() {
    int i;
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    cin >> n >> m;

    for(i = 1; i <= m; ++i) {
        cin >> a[i] >> b[i];
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);

        gr[a[i]]++; gr[b[i]]++;
    }

    for(i = 1; i <= n; ++i) {
        it[i] = v[i].begin();

        if(gr[i] & 1) {
            cout << "-1\n";
            return 0;
        }
    }

    eul(1);

    for(i = 0; i < rez.size() - 1; ++i)
        cout << rez[i] << " ";

    return 0;
}