#include <iostream>
#include <cstdio>
#include <vector>

using namespace std;

vector <int> v[100010],st,ans;
int n,m,i,j;

int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    cin>>n>>m;
    for (i=1; i<=m; i++)
    {
        int a,b;
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    for (i=1; i<=n; i++)
        if (v[i].size()%2!=0||v[i].size()==0)
        {
            cout << "-1\n";
            return 0;
        }
    int x;
    st.push_back(1);
    while (st.size()>0)
    {
        x=st[st.size()-1];
        while (v[x].size()>0)
        {
            int y=v[x][v[x].size()-1];
            v[x].pop_back();
            int gasit=0;
            for (int j=0; j<v[y].size()&&!gasit; j++)
                if (v[y][j]==x)
                {
                    swap(v[y][j],v[y][v[y].size()-1]);
                    v[y].pop_back();
                    gasit=1;
                }
            st.push_back(y);
            x=y;
        }
            st.pop_back();
            ans.push_back(x);
    }
    for (i=0; i<ans.size()-1; i++)
        cout << ans[i] << ' ';
}