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

#define NMAX 100001

int n,m;
vector<int>g[NMAX];
bitset<NMAX>b;
struct HASH{
    template<typename T>
    size_t operator()(T vl)const{
        hash<int>h;
        return size_t(h(vl.first))^size_t(h(vl.second));
    }
};
unordered_map<pair<int,int>,int,HASH>mucs;
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{
    for(auto it:g[i]){
        if(mucs[{i,it}]){
            --mucs[{i,it}];
            --mucs[{it,i}];
            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].push_back(y);
        g[y].push_back(x);
        mucs[{x,y}]++;
        mucs[{y,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;
}