#include <bits/stdc++.h>
#define MAXN 100000
#define MAXM 500000

using namespace std;

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

vector <pair<int, int>> graf[MAXN + 1];
int grad[MAXN + 1], viz[MAXM + 1];

void euler(int nod){
    int i;

    for(i = 1; i < graf[nod].size(); i++){
        if(viz[graf[nod][i].second] == 0){
            viz[graf[nod][i].second] = 1;
            euler(graf[nod][i].first);
        }
    }
    fout << nod << " ";
}

int main()
{
    int n, m, i, a, b;

    fin >> n >> m;

    for(i = 1; i <= m; i++){
        fin >> a >> b;
        grad[a]++;
        grad[b]++;
        graf[a].push_back({b, i});
        graf[b].push_back({a, i});
    }

    i = 1;
    while(i <= n && grad[i] % 2 == 0){
        i++;
    }
    if(i <= n){
        fout << "-1\n";
    }else{
        euler(1);
        fout << "\n";
    }
    return 0;
}