#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

#define NMax 100005
#define MMax 500005

ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");

int n,m;

struct nod
{
    int v,w,t;

    bool operator < (const nod &x) const
    {
        return x.t < t;
    }
};

nod add(int v,int w,int t)
{
    nod u;
    u.v = v;
    u.w = w;
    u.t = t;
    return u;
}

vector<nod> v[NMax];
bool viz[NMax];
int used[MMax];
bool euler = true;
int visited;
int start[NMax];

void DFS(int x)
{
    ++visited;
    if(v[x].size() % 2 == 1)  euler = false;

    viz[x] = true;
    for(int i=0;i<v[x].size();++i) if(!used[v[x][i].w])
    {
        if(!viz[v[x][i].v]) v[x][i].t = 1;
        else v[x][i].t = 2;

        used[v[x][i].w] = v[x][i].t;

        if(!viz[v[x][i].v]) DFS(v[x][i].v);
    }
    else v[x][i].t = used[v[x][i].w];
}

void DFS2(int x)
{
    if(m-- > 0) g<<x<<" ";

    for(int i=start[x];i<v[x].size();++i) if(used[v[x][i].w])
    {
        start[x] = i+1;
        used[v[x][i].w] = false;
        return DFS2(v[x][i].v);
    }
}

int main()
{
    int i,a,b;

    f>>n>>m;
    for(i=1;i<=m;++i)
    {
        f>>a>>b;
        v[a].push_back(add(b,i,0));
        v[b].push_back(add(a,i,0));
    }

    DFS(1);
    if(euler == false || visited != n) g<<"-1\n";
    else
    {
        for(i=1;i<=n;++i) sort(v[i].begin(),v[i].end());
        DFS2(1);
    }

    f.close();
    g.close();
    return 0;
}