#include <cstdio>
#include <vector>
#define N 100010
#define M 500010
using namespace std;
vector <int> v[N];
int a[M],b[M],aux,i,n,m,gr[N];
bool viz[M],q[M];
void dfs(int nod)
{
    for(vector <int>::iterator it=v[nod].begin();it!=v[nod].end();it++)
    {
        int vec=a[*it]+b[*it]-nod;
        if(!viz[vec])
        {
            viz[vec]=1;
            q[*it]=1;
            dfs(vec);
        }
    }
}
void go(int nod)
{
    if(m){printf("%d ",nod);m--;}
    else
        return;
    int vec=a[v[nod].back()]+b[v[nod].back()]-nod;
    while(m&&v[nod].size()&&vec==nod)
    {
        printf("%d ",nod);m--;
        v[nod].pop_back();
         vec=a[v[nod].back()]+b[v[nod].back()]-nod;
    }
    while(v[nod].size())
    {
        int muchie=v[nod].back();
        if(viz[muchie]){v[nod].pop_back();continue;}
        viz[muchie]=1;
        v[nod].pop_back();
        go(a[muchie]+b[muchie]-nod);
    }
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&a[i],&b[i]);
        v[a[i]].push_back(i);
        v[b[i]].push_back(i);
        gr[a[i]]++;
        gr[b[i]]++;
    }
    for(i=1;i<=n;i++)
        if(gr[i]&1)
        {
            printf("-1\n");
            return 0;
        }
    viz[1]=1;
    dfs(1);
    for(i=1;i<=n;i++)
    {
        if(!viz[i])
        {
            printf("-1\n");
            return 0;
        }
        viz[i]=0;
    }
    for(i=1;i<=n;i++)
    {
        int L,R;L=0;R=v[i].size()-1;
        do
        {
            while(L<R&&q[v[i][L]])L++;
            while(L<R&&!q[v[i][R]])R--;
            if(L<R){aux=v[i][L];v[i][L]=v[i][R];v[i][R]=aux;L++,R--;}

        }while(L<R);
    }
    go(1);
    return 0;
}