#include <cstdio>
#include <vector>
#include <stack>
#define nmax 100001

using namespace std;

int n, m;
int Grad[nmax];
vector <int> G[nmax];
stack <int> s, sol;

FILE *fi, *fo;

bool gradImpar()
{
    for (int i = 1; i <= n; i++)
        if (Grad[i] % 2 == 1)
            return 1;
    return 0;
}

void sterge(int deSters, int nod)
{
    for (vector <int> :: iterator it = G[nod].begin(); it != G[nod].end(); ++it)
        if (*it == deSters)
        {
            G[nod].erase(it);
            return;
        }
}

void euler(int nod)
{
    s.push(nod);
    while (!s.empty()){
        int nod = s.top();
        if (G[nod].size())
        {
            int vecin = G[nod][0];
            G[nod].erase(G[nod].begin());
            sterge(nod, vecin); // sterge nodul din vecinii veciniului
            s.push(vecin);
        }
        else
        {
            sol.push(nod);
            s.pop();
        }
    }
}

int main()
{
    
    fi = fopen("ciclueuler.in", "r");
    fo = fopen("ciclueuler.out", "w");
    
    fscanf(fi, "%d%d", &n, &m);
    
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        fscanf(fi, "%d%d", &x, &y);
        G[x].push_back(y);
        G[y].push_back(x);
        Grad[x]++, Grad[y]++;
    }
    
    if (gradImpar())
    {
        fprintf(fo, "%d\n", -1);
        return 0;
    }
    
    euler(1);
    
    while (sol.size() > 1)
    {
        fprintf(fo, "%d ", sol.top());
        sol.pop();
    }
    
    fclose(fi);
    fclose(fo);
    
    return 0;
}