#include <bits/stdc++.h>

using namespace std;

FILE*f=fopen("ciclueuler.in","r");
FILE*g=fopen("ciclueuler.out","w");

stack<int>s;
list<pair<int,int> >l[100010];
list<int>::iterator it;
int b[500010];

int main()
{
    int n,m,i,x=1,y,ok,j,k;
    fscanf(f,"%d%d",&n,&m);
    for (i=1;i<=m;i++){
        fscanf(f,"%d%d",&x,&y);
        l[x].push_back(make_pair(y,i));
        l[y].push_back(make_pair(x,i));
    }
    ok=1;
    for (i=1;i<=n;i++)
        if (l[i].size()%2==1) {ok=0;break;}
    if (!ok) fprintf(g,"-1");
    else{

    s.push(1);
    while (!s.empty()){
        i=s.top();ok=l[i].size();
        if (!l[i].empty()){
            j=l[i].back().first;
            k=l[i].back().second;
            l[i].pop_back();
            if (!b[k]){
                b[k]=1;
                s.push(j);
            }
        }
        else{
        if (s.size()!=1) fprintf(g,"%d ",i);
        s.pop();
        }
    }
    }
    fclose(f);
    fclose(g);
    return 0;
}