#include <iostream>
#include <vector>
using namespace std;
int megoldas()
{
	int m;
	cin >> m;
	vector<int> pontok(1, 0);
	vector<int> rosszHelyek;
	vector<vector<int>> elek(m + 1, vector<int>(0, 0));
	for (int j = 0; j < m; j++)
	{
		int t;
		cin >> t;
		pontok.push_back(t);
		if (t == -1) rosszHelyek.push_back(j + 1);
	}
	for (int j = 0; j < m - 1; j++)
	{
		int a, b;
		cin >> a >> b;
		elek[a].push_back(b);
		elek[b].push_back(a);
	}
	for (int j : rosszHelyek)
	{
		for (int csucs : elek[j])
		{
			if (pontok[csucs] == -1)
			{
				cout << "NEM" << endl << 2 << endl << j << " " << csucs << endl;
				return 0;
			}
			else
			{
				for (int harmadik : elek[csucs])
				{
					if (pontok[harmadik] == -1 && harmadik != j)
					{
						cout << "NEM" << endl << 3 << endl << j << " " << csucs << " " << harmadik << endl;
						return 0;
					}
				}
			}
		}
	}
	cout << "IGEN" << endl;
	return 0;
}
int main()
{
	int n;
	cin >> n;
	for (size_t i = 0; i < n; i++)
	{
		megoldas();
	}
	return 0;
}
/*
2
4
-1 1 -1 -1
1 4
1 2
1 3
5
-1 1 1 -1 1
1 2
2 3
3 4
4 5
*/