#include <bits/stdc++.h>

using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
const int M = 500010;
const int N = 100010;
int n,m,i,a[M],b[M],gr[N];
bitset<M> used,tree;
bitset<N> viz;
vector<int> v[N];
void dfs(int),go(int);
int main()
{
    f>>n>>m;
    for(i=1; i<=m; i++)
    {
        f>>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]%2)
        {
            g<<"-1\n";
            return 0;
        }
    dfs(1);
    for(i=1; i<=n; i++)
        if(!viz[i])
        {
            g<<"-1\n";
            return 0;
        }
    for(i=1;i<=n;i++)
    {
        int st=0;
        int dr=v[i].size()-1;
        while(st<dr)
        {
            if(tree[v[i][st]])
                st++;
            else
                if(!tree[v[i][dr]])
                    dr--;
            else
                swap(v[i][st++],v[i][dr--]);
        }
    }
    go(1);
    return 0;
}
void dfs(int nod)
{
    viz[nod]=1;
    for(auto it:v[nod])
    {
        int vec=a[it]+b[it]-nod;
        if(!viz[vec])
        {
            tree[it]=1;
            dfs(vec);
        }
    }
}
void go(int nod)
{
    while(v[nod].size()&&used[v[nod].back()])
        v[nod].pop_back();
    if(!v[nod].size())
        return;
    g<<nod<<' ';
    int edge=v[nod].back();
    v[nod].pop_back();
    used[edge]=1;
    nod=a[edge]+b[edge]-nod;
    go(nod);
}