#include<iostream>
#include<vector>
#include<unordered_set>
#include<bitset>
using namespace std;

#define NMAX 100001

int n,m;
unordered_set<int>g[NMAX];
bitset<NMAX>b;
auto check_dfs(int i)->void{
    b[i]=true;
    if(g[i].size()%2){
        // nu poate fi ciclu euleria pt ca nodul i are nr de vecini impar
        cout<<-1;
        exit(0);
    }
    for(auto it:g[i]){
        if(b[it])continue;
        check_dfs(it);
    }
}
vector<int>sol;
auto euler(int i)->void{
    while(g[i].size()){
        int it=*g[i].begin();
        g[i].erase(g[i].begin());
        auto rm=g[it].find(i);
        g[it].erase(rm);
        euler(it);
    }
    sol.push_back(i);
}
auto main(void)->signed{
    #ifndef LOCAL
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        cout.tie(nullptr);
    #endif
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    cin>>n>>m;
    for(int i=1;i<=m;++i){
        int x,y;
        cin>>x>>y;
        g[x].insert(y);
        g[y].insert(x);
    }
    // daca fiecare nod din graf are un nr par de vecini acela e ciclu eulerian
    // altfel nu e
    check_dfs(1);
    euler(1);
    if(sol.size()>1)sol.pop_back();
    for(auto it:sol)cout<<it<<" ";
    return 0;
}