#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#include <queue>
#define maxn 100005
using namespace std;

int n,m,dg[maxn],viz[maxn];
vector <int > g[maxn],fin;
stack < int > st;
queue <int > q;
void citesc ()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        g[x].push_back(y);
        g[y].push_back(x);
        dg[x]++;
        dg[y]++;
    }
}

void bfs()
{
    q.push(1);
    while (!q.empty())
    {
        int nod=q.front();
        q.pop();
        for (vector <int > :: iterator it=g[nod].begin();it!=g[nod].end();++it)
            if (!viz[*it])
        {
            viz[*it]=1;
            q.push(*it);
        }
    }
}
bool e_conex()
{
    bfs();
    for (int i=1;i<=n;++i)
        if (!viz[i])
            return 0;
    return 1;
}
bool euler()
{
    if (!e_conex())
        return 0;
    for (int i=1;i<=n;++i)
        if (dg[i]%2!=0)
        return 0;
    return 1;
}
void rez(int v)
{
    while (1)
    {
        if (g[v].empty())
            break;
        int w=g[v].front();
        st.push(v);
        for (vector <int > :: iterator it=g[w].begin();it!=g[w].end();++it)
            if (*it==v)
        {
            g[w].erase(it);
            break;
        }
        g[v].erase(g[v].begin());
        v=w;
    }
}
void solv()
{
    if (euler()==0)
    {
        printf("-1");
        return;
    }
    int v=1;
    do
    {
        rez(v);
        v=st.top();
        st.pop();
        fin.push_back(v);
    }
    while (!st.empty());
    for (vector <int > :: iterator it=fin.begin();it!=fin.end();++it)
        printf("%d ",*it);
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citesc();
    solv();
    return 0;
}