#include <fstream>
#include <stack>
#include <vector>

using namespace std;

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

vector<pair<int, int>> L[100005];
stack<int> stiva;
int f[100005], grad[100005];
int n, m, x, y;

void dfs (int nod) {
    f[nod] = 1;
    for (auto it: L[nod]) {
        int vecin = it.first;
        if (f[vecin] == 0){
            dfs(vecin);
        }
    }
}

int main(){
    fin >> n >> m;
    for (int i=0; i<m; i++){
        fin >> x >> y;
        L[x].push_back({y, i});
        L[y].push_back({x, i});
        grad[x]++, grad[y]++;
    }
    dfs(1);
    for (int i=1; i<=n; i++){
        if (f[i] == 0 || grad[i] % 2 != 0){
            fout << -1;
            return 0;
        }
    }

    stiva.push(1);
    for (int i=0; i<=n; i++){
        f[i] = 0;
    }

    while (!stiva.empty()){
        int nod = stiva.top();

        if (grad[nod] == 0){ ///nod epuizat
            if (stiva.size() != 1){
                fout << nod << ' ';
            }
            stiva.pop();
            continue;
        }

        while (f[L[nod].back().second] == 1){
            L[nod].pop_back();
        }
        int vecin = L[nod].back().first;
        int muchie = L[nod].back().second;
        f[muchie] = 1;
        stiva.push(vecin);
        grad[nod]--, grad[vecin]--;
        L[nod].pop_back();
    }
    return 0;
}