#include <fstream>
#include <list>
#include <stack>
#include <queue>
#define NMAX 100010

using namespace std;

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

int n, m, grades[NMAX];
bool vis[NMAX];
list <int> a[NMAX], f;
stack <int> S;

void read();
int check();
void BFS();
void euler(int v);
void deletee(int c, int next);
void solve();

int main()
{
    read();
    if(check() == 0)
    {
        fout << -1 << '\n';
        return 0;
    }
    else
    {
        solve();
        while(!f.empty())
        {
            fout << f.front()<< ' ';
            f.pop_front();
        }
        fout << '\n';
    }
    return 0;
}

void read()
{
    int i, x, y;
    fin >> n >> m;
    for(i = 1; i <= m; i++)
    {
        fin >> x >> y;
        ++grades[x];
        a[x].push_back(y);
        ++grades[y];
        if(x != y)
        a[y].push_back(x);
    }
}

void BFS()
{
    queue <int> Q;
    int v;
    Q.push(1);
    vis[1] = 1;
    while(!Q.empty())
    {
        v = Q.front();
        Q.pop();
        for(std::list<int>::iterator i = a[v].begin(); i != a[v].end(); i++)
            if(vis[*i] != 1)
            {
                Q.push(*i);
                vis[*i] = 1;
            }
    }
}

int check()
{
    int i;
    BFS();
    for(i = 1; i <= n; i++)
        if(vis[i] == 0)
        return 0;
    for(i = 1; i <= n; i++)
        if(grades[i] % 2 == 1)
        return 0;
    return 1;
}

void euler(int v)
{
    int c = v, next;
    while(!a[c].empty())
    {
        next = a[c].front();
        S.push(c);
        deletee(c, next);
        c = next;
    }
}
void deletee(int c, int next)
{
    a[c].pop_front();
    for(std::list<int>::iterator i = a[next].begin(); i != a[next].end(); i++)
        if(*i == c)
        {
            a[next].erase(i);
            break;
        }
}

void solve()
{
    int v = 1;
    do
    {
        euler(v);
        v = S.top();
        S.pop();
        f.push_front(v);
    }while(!S.empty());
}