#include <iostream>
#include<stack>
#include<vector>
#include<fstream>
using namespace std;
vector<vector<pair<int,int>>>mu;
int n,x,y,i,j,ans[500005],cnt,fr[50005],m,unde[50005];
stack<int>st;
void DFS(int nod){
    for(unsigned int z=unde[nod];z<mu[nod].size();++z)
    {
        int nxt=mu[nod][z].first;
        int nr=mu[nod][z].second;
        if(fr[nr]==0){
            unde[nod]=z+1;
            fr[nr]=1;
            st.push(nxt);
            nod=nxt;
        z=unde[nod]-1;
        }
    }
}
int main()
{
    ifstream cin("ciclueuler.in");
    ofstream cout("ciclueuler.out");
    cin>>n>>m;
    mu.resize(n+2);
    for(i=1;i<=m;i++)
    {
        cin>>x>>y;
        mu[x].push_back({y,i});
        mu[y].push_back({x,i});
    }
    for(i=1;i<=n;i++)
        if((mu[i].size()&1) or mu[i].size()==0)
    {
        cout<<-1;
        return 0;
    }
    st.push(1);
    while(st.empty()!=1){
        int x=st.top();
        DFS(x);
        ans[++cnt]=st.top();
        st.pop();
    }
    if(cnt-1!=m)
    {
        cout<<-1;
        return 0;
    }
    for(i=1;i<cnt;i++)
        cout<<ans[i]<<" ";
}