#include<bits/stdc++.h>
using namespace std;
const int MAX=1e5+5;
vector<int> g[MAX];
struct edge{
    int from,to;
};
edge e[MAX];
int n,m,fa[MAX];
stack<int> st;
bool flag,vis[MAX];
map<pair<int,int>,int> edg;
int ans[MAX],cnt,anse[MAX];
void dfs(int u,int fr){
    if(flag)
        return;
    st.push(u);
    for(auto i=g[u].begin();i!=g[u].end();++i){
        int v=(*i);
        if(v==fr||v==u)
            continue;
        if(flag)
            return;
        if(vis[v]){
            flag=1;
            while(st.top()!=v){
                ans[++cnt]=st.top();
                st.pop();
            }
            ans[++cnt]=v;
            return;
        }
        else{
            vis[v]=1;
            dfs(v,u);
        }
    }
    if(flag)
        return;
    st.pop();
}
int findf(int x){
    if(fa[x]==x)
        return x;
    fa[x]=findf(fa[x]);
    return fa[x];
}
void solve(){
    edg.clear();
    while(!st.empty())
        st.pop();
    cnt=0;
    flag=0;
    cin>>n>>m;
    for(int i=1;i<=n;++i){
        fa[i]=i;
    }
    memset(vis,0,sizeof(bool)*(n+1));
    for(int i=1;i<=n;++i)
        g[i].clear();

    for(int i=1;i<=m;++i){
        cin>>e[i].from>>e[i].to;
        if(!edg[make_pair(e[i].from,e[i].to)]){
            edg[make_pair(e[i].from,e[i].to)]=i;
            edg[make_pair(e[i].to,e[i].from)]=i;
        }
    }

    int tot=0;
    for(int i=1;i<=m;++i){
        tot=i;
        int r1=findf(e[i].from),r2=findf(e[i].to);
        if(r1!=r2){
            fa[r2]=r1;
        }
        else{
            break;
        }
    }

    for(int i=1;i<=tot;++i){
        g[e[i].from].push_back(e[i].to);
        g[e[i].to].push_back(e[i].from);
    }

    for(int i=1;i<=n;++i){
        if(!vis[i]&&!flag){
            vis[i]=1;
            dfs(i,0);
        }
    }
    if(flag){
        anse[1]=edg[make_pair(ans[1],ans[2])];
        for(int i=2;i<=cnt-1;++i){
            anse[i]=edg[make_pair(ans[i],ans[i+1])];
        }
        anse[cnt]=edg[make_pair(ans[cnt],ans[1])];

        sort(anse+1,anse+1+cnt);
        cout<<anse[1];
        for(int i=2;i<=cnt;++i)
            cout<<" "<<anse[i];
        cout<<"\n";
    }
    else{
        cout<<"-1\n";
    }
}
int main(){
//    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);

    int T;
    cin>>T;
    while(T--){
        solve();
    }
}