#include <fstream>
#include <vector>
#include <algorithm>
#include <bitset>
#include <stack>
#define DIM 100004

using namespace std;

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

int N, M;

int node;

bitset <DIM> viz;

vector <int> V[DIM];

stack <int> capita;

int check1(){
    for(int i=1;i<=N;i++)
        if(V[i].size()%2!=0)
            return 0;
    return 1;
}
void dfs(int x){
    viz[x]=1;
    for(int i=0;i<V[x].size();i++)
        if(!viz[V[x][i]])
            dfs(V[x][i]);
}
int check2(){
    dfs(1);
    for(int i=2;i<=N;i++)
        if(!viz[i])
            return 0;
    return 1;
}

int main(){

    fin >> N >> M;

    while(M--){
        int x,y;
        fin >> x >> y;
        V[x].push_back(y);
        V[y].push_back(x);
    }

    if(!(check1() && check2())){
        fout << "-1\n";
        return 0;
    }

    node = 1;

    capita.push(1);

    while(!capita.empty()){
        node = capita.top();
        if(!V[node].size()){
            fout << node << " ";
            capita.pop();
        }
        else{
            int x = V[node].back();
            capita.push(x);
            V[node].pop_back();
            V[x].erase(find(V[x].begin(), V[x].end(), node));
        }
    }

    return 0;
}