#include <bits/stdc++.h>

using namespace std;

#define ll long long

const int N = 1e5 + 5;

int deg[N];
vector <int> edge[N];
queue < pair < int, int > > edgeQ[N];
bool viz[N];
bool used[5 * N];

vector <int> ans;

void dfs(int x){
    viz[x] = true;
    for(auto &it : edge[x]){
        if(viz[it] == false){
            dfs(it);
        }
    }
}

void dfsEuler(int x){
    while(edgeQ[x].empty() == false && used[edgeQ[x].front().second] == 1){
        edgeQ[x].pop();
    }
    while(edgeQ[x].empty() == false){
        auto f = edgeQ[x].front();
        edgeQ[x].pop();
        used[f.second] = true;
        dfsEuler(f.first);
    }
    ans.push_back(x);
}

int main(){
//    ios_base::sync_with_stdio(false);
//    cin.tie(0);
//    cout.tie(0);
    ifstream fin("ciclueuler.in");
    ofstream fout("ciclueuler.out");
    int n, m;
    fin >> n >> m;
    for(int i = 1;i <= m;i++){
        int x, y;
        fin >> x >> y;
        edge[x].push_back(y);
        edgeQ[x].push({y, i});
        edge[y].push_back(x);
        edgeQ[y].push({x, i});
        deg[x]++;
        deg[y]++;
    }
    dfs(1);
    for(int i = 1;i <= n;i++){
        if(viz[i] == 0 || deg[i]%2 == 1){
            fout << -1;
            return 0;
        }
    }
    dfsEuler(1);
    for(auto &it : ans){
        fout << it << ' ';
    }
	return 0;
}