#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 2e5;
const int MMAX = 5e5;

struct ura{
    
    int a, b;
    
};

ura muchii[MMAX + 1];
vector<int> adj[NMAX + 1], rez;
int grad[NMAX + 1];

bool deleted[MMAX + 1]; //aflam daca muchia a fost sau nu stearsa

int next(int nod){
    
    while(!adj[nod].empty() and deleted[adj[nod][adj[nod].size() - 1]])
        adj[nod].pop_back();
        
    if(adj[nod].empty())
        return 0;
        
    deleted[adj[nod][adj[nod].size() - 1]] = true;
    
    return muchii[adj[nod][adj[nod].size() - 1]].a + muchii[adj[nod][adj[nod].size() - 1]].b - nod;
    
}

void euler(int nod){
    
    while(int c = next(nod))
        euler(c);
        
    rez.push_back(nod);
    
}

int main()
{
    
    int n, m;
    f >> n >> m;
    
    for(int i=1; i<=m; i++){
        
        int x, y;
        f >> x >> y;
        
        muchii[i] = {x, y};
        
        adj[x].push_back(i);
        adj[y].push_back(i);
        
        grad[x] ++;
        grad[y] ++;
        
    }
    
    euler(1);
    
    //cout << rez.size();
    
    for(int i=1; i<=n; i++)
        if(grad[i] % 2){
            
            g << -1;
            return 0;
            
        }
    
    if(rez.size() != m + 1){
        
        g << -1;
        return 0;
        
    }
    
    for(int i=0; i<rez.size()-1; i++)
        g << rez[i] << ' ';

    return 0;
}