import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.TreeSet;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Jaynil
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskE solver = new TaskE();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class TaskE {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int m = in.nextInt();
            ArrayList<int[]> edges = new ArrayList<>();
            TreeSet<Integer> ts = new TreeSet<>();
            ArrayList<Integer> mat = new ArrayList<>();
            for (int i = 0; i < m; i++) {
                edges.add(new int[]{in.nextInt(), in.nextInt()});
            }
            for (int i = 0; i < m; i++) {
                if (mat.size() == n) break;
                if (!ts.contains(edges.get(i)[0]) && !ts.contains(edges.get(i)[1])) {
                    mat.add(i + 1);
                    ts.add(edges.get(i)[0]);
                    ts.add(edges.get(i)[1]);
                }
            }
            if (mat.size() == n) {
                out.println("Matching");
                for (int i = 0; i < n; i++) {
                    out.print(mat.get(i) + " ");
                }
            } else {
                out.println("IndSet");
                int c = 0;
                for (int i = 1; i <= 3 * n; i++) {
                    if (c == n) break;
                    if (!ts.contains(i)) {
                        out.print((i) + " ");
                        c++;
                    }
                }
            }
            out.println();
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}

