#include <fstream>
#include <vector>
#include <unordered_set>

using namespace std;

ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
int n, m;
unordered_multiset<int> v[100005];
vector<int> ans;

void dfs(int nod)
{
    while(!v[nod].empty())
    {
        int nxt = *v[nod].begin();
        v[nod].erase(v[nod].find(nxt));
        v[nxt].erase(v[nxt].find(nod));

        dfs(nxt);
    }

    ans.push_back(nod);
}

int main()
{
    in>>n>>m;

    int x, y;
    for(int i = 1; i<=m; i++)
    {
        in>>x>>y;

        v[x].insert(y);
        v[y].insert(x);
    }

    for(int i = 1; i<=n; i++)
    {
        if(v[i].size() % 2 == 1)
        {
            out<<-1;
            return 0;
        }
    }

    dfs(1);

    ans.pop_back();
    for(auto it: ans)
    {
        out<<it<<" ";
    }

    return 0;
}