#include <bits/stdc++.h>
#define pb push_back
#define N 100005

using namespace std;
vector<int>v[N], q;
bitset<N>viz;
int n, m, x, y, i, nod, vec;
void df(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    for(auto it : v[nod])
        df(it);
}
int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    scanf("%d%d", &n, &m);
    for(; m; m--)
    {
        scanf("%d%d", &x, &y);
        v[x].pb(y);
        v[y].pb(x);
    }
    for(i = 1; i <= n; i++)
        if(v[i].size() & 1)
        {
            printf("-1");
            return 0;
        }
    df(1);
    for(i = 1; i <= n; i++)
        if(!viz[i])
        {
            printf("-1");
            return 0;
        }
    q.pb(1);
    while(q.size())
    {
        nod = q.back();
        if(v[nod].size())
        {
            vec = v[nod].back();
            q.pb(vec);
            v[nod].pop_back();
            for(auto&it : v[vec])
                if(it == nod)
                {
                    it = v[vec].back();
                    v[vec].pop_back();
                    break;
                }
        }
        else
        {
            q.pop_back();
            printf("%d ", nod);
        }
    }
    return 0;
}