#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

std::ifstream in("ciclueuler.in");
std::ofstream out("ciclueuler.out");

const int N=100000;
const int M=500000;

std::pair<int, int> e[M+1];
bool visited[M+1];

std::vector<int> v[N+1];
std::vector<int> ans;
std::stack<int> q;

int n, m;

int main()
{
    int x, y;

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

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

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

    q.push(1);
    while(!q.empty())
    {
        int i=q.top();

        bool flag=false;

        for(int muchii : v[i])
        {
            if(!visited[muchii])
            {
                flag=true;
                visited[muchii]=true;
                q.push(e[muchii].first+e[muchii].second-i);
                break;
            }
        }

        if(!flag)
        {
            q.pop();
            if(!q.empty())
            {
                ans.push_back(i);
            }
        }
    }

    if(ans.size()<m)
    {
        out<<-1;
        return 0;
    }

    for(int contor : ans)
    {
        out<<contor<<" ";
    }

    return 0;
}