#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define MAX(a, b) (a) = max((a), (b))
#define MIN(a, b) (a) = min((a), (b))
#define all(a) (a).begin(), (a).end()
#define sortedpair(a, b) {min((a), (b)), max((a), (b))}

const ll MOD = 1e9+7;

void solve(){
    int n, m; cin>>n>>m;
    set<pair<int, int>> s;
    for(int i = 0; i < m; i++){
        int a, b; cin>>a>>b;
        if(a>b)swap(a,b);
        s.insert({a, b});
    }
    assert(s.size() == m);
    cout<<-1<<endl;
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int _t = 1;
    cin >> _t;
    while (_t--) {
        solve();
    }
    return 0;
}