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

using namespace std;

ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
int n, m;
vector<pair<int, int>> v[100005];
int used[500005];
vector<int> ans;

void dfs(int nod)
{
    while(!v[nod].empty())
    {
        pair<int, int> nxt = v[nod].back();

        v[nod].pop_back();

        if(used[nxt.second] == 0)
        {
            used[nxt.second] = 1;
            dfs(nxt.first);
        }
    }

    ans.push_back(nod);
}

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

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

        v[x].push_back({y, i});
        v[y].push_back({x, i});
    }

    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;
}