// Source: https://usaco.guide/general/io

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

int main() {
	int t;
	cin >> t;
	while (t--) {
		int n;
		cin >> n;
		vector<int> jo(n), db(n);
		for (int i = 0; i < n; i++) {
			cin >> jo[i];
		}


		bool found = false;
		for (int i = 0; i < n - 1; i++) {
			int a, b;
			cin >> a >> b;
			if ((jo[a - 1] == -1 && jo[b - 1] == -1) && !found) {
				cout << "NEM\n2\n" << a << " " << b << "\n";
				found = true;
			}
			
			if ((db[a - 1] != 0 && jo[b - 1] == -1) && !found) {
				cout << "NEM\n3\n" << db[a - 1] << " " << a << " " << b << "\n";
				found = true;
			}

			if ((db[b - 1] != 0 && jo[a - 1] == -1) && !found) {
				cout << "NEM\n3\n" << db[b - 1] << " " << b << " " << a << "\n";
				found = true;
			}

			if (jo[a - 1] == -1) {
				db[b - 1] = a;
			}

			if (jo[b - 1] == -1) {
				db[a - 1] = b;
			}
		}

		if (!found) cout << "IGEN" << "\n";
	}
}