#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 100005;
int n,m, was[NMAX], viz[NMAX], Stack[5 * NMAX];
vector < pair < int, int > > v[NMAX];

void dfs(int node){
    viz[node] = 1;
    for(auto it: v[node])
        if(!viz[it.first])
            dfs(it.first);
}

int main(){
    int i,x,y,root;
    f >> n >> m;
    for(i = 1 ; i <= m ; i++){
        f >> x >> y;
        v[x].push_back(make_pair(y,i));
        v[y].push_back(make_pair(x,i));
        was[x]++;
        was[y]++;
    }

    for(i = 1 ; i <= n ; i++)
        if(was[i]){
            dfs(i);
            root = i;
            i = n;
        }

    for(i = 1 ; i <= n ; i++){
        if(was[i] && !viz[i]){
            g << -1;
            return 0;
        }
        viz[i] = 0;
    }

    int elem = 1, node, neighbour;
    Stack[1] = root;
    bool ok = 0;
    while(elem){
        node = Stack[elem];
        if(!was[node]){
            if(ok){
                g << node << " ";
                elem--;
                continue;
            }else{
                ok = 1;
                elem--;
                continue;
            }
        }

        while(!v[node].empty() && viz[v[node].back().second] == 1)
            v[node].pop_back();

        neighbour = v[node].back().first;
        was[node]--;
        was[neighbour]--;
        viz[v[node].back().second] = 1;
        v[node].pop_back();
        Stack[++elem] = neighbour;
    }

    return 0;
}