#include <bits/stdc++.h>

using namespace std;

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

int n, m, i, nod, vecin, k, x, y;
int p[100005], q[500005], f[500005];

vector <pair <int, int> > L[100005];

inline void dfs (int nod){
    int vecin;
    f[nod]=1;
    for(int i=0; i<L[nod].size(); i++){
        vecin = L[nod][i].first;
        if(f[vecin] == 0)
            dfs(vecin);
    }
}

int main(){
    fin >> n >> m;
    for (i=1; i<=m; i++){
        fin >> x >> y;
        L[x].push_back ({y, i});
        L[y].push_back ({x, i});
        p[x]++, p[y]++;
    }
    dfs (1);
    for (i=1; i<=n; i++){
        if (!f[i] || p[i]%2){
            fout << -1;
            return 0;
        }
    }
    for (i=1; i<=n; i++){
        f[i] = 0;
    }
    q[++k] = 1;
    while (k){
        nod = q[k];
        if (!p[nod]){
            if (k != 1){
                fout << nod << " ";
            }
            k--;
            continue;
        }
        while (f[L[nod].back().second] == 1){
            L[nod].pop_back();
        }
        vecin = L[nod].back().first;
        q[++k] = vecin;
        f[L[nod].back().second] = 1;
        L[nod].pop_back();
        p[nod]--, p[vecin]--;
    }
    return 0;
}