#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 2e5 + 5;

int n, m;

int T;

int a[N], b[N];

int t[N];

set < int > num1, num2;

main ()
{
	cin >> T;

	while (T --)
	{
		num1.clear () , num2.clear ();
		
		cin >> n >> m;

		for (int i = 1; i <= m; i ++)
			cin >> a[i] >> b[i];
		
		for (int i = 1;i <= m;i ++)
		{
			if (a[i] == 1)
				num1.insert (b[i]);
			else if (a[i] == 2)
				num2.insert (b[i]);
			
			if (num1.size() == n || num2.size () > 1 || a[i] == 2 && num1.count (b[i]))
			{
				cout << i << '\n';
				
				goto lop;
			}
		}	
				
		
		cout << -1 << '\n';
		
		lop :
			continue;
	}
}