#include <cstdio>
#include <cstring>
#include <vector>
#include <deque>
#include <algorithm>
#define maxN 100002
using namespace std;
int n, i, j, m, ok, x, y;
deque < int > q;
vector < int > V[maxN];
bool vis[maxN];
void read()
{
    freopen("ciclueuler.in", "r", stdin);
    scanf("%d %d", &n, &m);
    while (m --)
    {
        scanf("%d %d", &x, &y);
        V[x].push_back(y);
        V[y].push_back(x);
    }
}
void dfs(int x)
{
    int i;
    vis[x] = 1;
    for (i = 0; i < V[x].size(); ++ i)
        if (!vis[V[x][i]])
           dfs(V[x][i]);
}
void solve()
{
    dfs(1);
    ok = 1;
    for (i = 1;i <= n;++ i)
    if (V[i].size() % 2 || !vis[i])
    {
        ok = 0;
        return ;
    }
}
void write()
{
    freopen("ciclueuler.out", "w", stdout);
    if (!ok)
    {
        printf("-1");
        return ;
    }
    q.push_back(1);
    while (!q.empty())
    {
        x = q.front();
        if (V[x].size() == 0)
        {
            q.pop_front();
            printf("%d ", x);
        }
        else
        {
            y = V[x].back();
            V[y].erase(find(V[y].begin(), V[y].end(), x));
            V[x].pop_back();
            q.push_front(y);
        }
    }
}
int main()
{
    read();
    solve();
    write();
    return 0;
}