#include<bits/stdc++.h>
using namespace std;
typedef long long int uli;
int rint(char nxt){
  char ch=getchar();
  int v=0;
  int sgn=1;
  if(ch=='-')sgn=-1;  
  else{
    assert('0'<=ch&&ch<='9');
    v=ch-'0';
  }
  while(true){
    ch=getchar();
    if('0'<=ch && ch<='9')v=v*10+ch-'0';
    else{
      assert(ch==nxt);
      break;
    }
  }
  return v*sgn;
}
const int mx=333;
vector<pair<int,int> >g[mx];
bool rem[mx*mx];//rem[i]=will edge i be removed?
int main(){
//  freopen("secret/0.in","r",stdin);
//  freopen("secret/0.out","w",stdout);
  int t=rint('\n');
  assert(1<=t&&t<=256);
  while(t--){
    int n=rint('\n');
    set<pair<int,int> >allEdges;
    for(int i=0;i<n;i++)g[i].clear();
    for(int i=0;i*2<n*(n-1);i++){
      int u=rint(' ');
      assert(1<=u&&u<=n);
      int v=rint('\n');
      assert(1<=v&&v<=n);
      //no loops
      assert(u!=v);
      g[--u].push_back(make_pair(--v,i));
      //no parallel edges
      assert(allEdges.count(make_pair(u,v))==0);
      assert(allEdges.count(make_pair(v,u))==0);
      allEdges.insert(make_pair(u,v));
      rem[i]=true;
    }
    if(__builtin_popcount(n)!=1){
      puts("-1");
      continue;
    }
    for(int i=0;i<n;i++){
      sort(g[i].begin(),g[i].end());
    }
    //lets start the tournament!
    vector<int>all(n);
    iota(all.begin(),all.end(),0);
    while(all.size()>0){
      vector<int>nxt;
      for(int i=0;i+1<int(all.size());i+=2){
        int u=all[i],v=all[i+1];
        int idx=lower_bound(g[u].begin(),g[u].end(),make_pair(v,-1))-g[u].begin();
        if(idx<int(g[u].size()) && g[u][idx].first==v){}
        else swap(u,v);
        //u beats v
        idx=lower_bound(g[u].begin(),g[u].end(),make_pair(v,-1))-g[u].begin();
        rem[g[u][idx].second]=false;
        nxt.push_back(u);
      }
      all=nxt;
    }
    vector<int>ans;
    for(int i=0;i*2<n*(n-1);i++)if(rem[i])ans.push_back(i);
    printf("%d\n",int(ans.size()));
    for(int i=0;i<int(ans.size());i++){
      if(i!=0)printf(" ");
      printf("%d",ans[i]+1);
    }
    puts("");
  }
  assert(getchar()==EOF);
  return 0;
}