#include <bits/stdc++.h>
#define MAXN 100001
#define MAXM 500001
using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
int n,m,to[MAXM],from[MAXM];
bool used[MAXM];
vector<int> v[MAXN], ans;
stack<int> stk;
int main()
{
    in>>n>>m;
    for(int i=1; i<=m; ++i)
    {
        int x,y;
        in>>x>>y;
        v[x].push_back(i);
        v[y].push_back(i);
        from[i]=x;
        to[i]=y;
    }
    for(int i=1; i<=n; ++i)
        if(v[i].size() & 1)
        {
            out<<-1;
            return 0;
        }
    stk.push(1);
    while(!stk.empty())
    {
        int nod=stk.top();
        if(!v[nod].empty())
        {
            int w=v[nod].back();
            v[nod].pop_back();
            if(!used[w])
            {
                used[w]=true;
                stk.push(from[w]^to[w]^nod);
            }

        }
        else
        {
            stk.pop();
            ans.push_back(nod);
        }
    }
    for(int i=0;i<ans.size()-1;++i)
        out<<ans[i]<<' ';
    return 0;
}