import java.io.*;
import java.nio.CharBuffer;
import java.util.ArrayList;
import java.util.NoSuchElementException;

public class P1199E {

    public static void main(String[] args) {
        SimpleScanner scanner = new SimpleScanner(System.in);
        PrintWriter writer = new PrintWriter(System.out);

        int caseNum = scanner.nextInt();
        while (caseNum-- > 0) {
            int n = scanner.nextInt();
            int m = scanner.nextInt();
            boolean[] covered = new boolean[3 * n];
            int[][] edges = new int[m][2];
            ArrayList<Integer> matchEdges = new ArrayList<>(m);
            for (int i = 0; i < m; ++i) {
                int u = scanner.nextInt() - 1;
                int v = scanner.nextInt() - 1;
                if (!covered[u] && !covered[v]) {
                    covered[u] = covered[v] = true;
                    matchEdges.add(i + 1);
                }
            }
            if (matchEdges.size() >= n) {
                writer.println("Matching");
                for (int i = 0; i < n; ++i)
                    writer.print(matchEdges.get(i) + " ");
            } else {
                writer.println("IndSet");
                for (int i = 0, cnt = 0; i < 3 * n; ++i)
                    if (!covered[i]) {
                        writer.print((i + 1) + " ");
                        if (++cnt == n)
                            break;
                    }
            }
            writer.println();
        }

        writer.close();
    }

    private static class SimpleScanner {

        private static final int BUFFER_SIZE = 10240;

        private Readable in;
        private CharBuffer buffer;
        private boolean eof;

        SimpleScanner(InputStream in) {
            this.in = new BufferedReader(new InputStreamReader(in));
            buffer = CharBuffer.allocate(BUFFER_SIZE);
            buffer.limit(0);
            eof = false;
        }


        private char read() {
            if (!buffer.hasRemaining()) {
                buffer.clear();
                int n;
                try {
                    n = in.read(buffer);
                } catch (IOException e) {
                    n = -1;
                }
                if (n <= 0) {
                    eof = true;
                    return '\0';
                }
                buffer.flip();
            }
            return buffer.get();
        }

        void checkEof() {
            if (eof)
                throw new NoSuchElementException();
        }

        char nextChar() {
            checkEof();
            char b = read();
            checkEof();
            return b;
        }

        String next() {
            char b;
            do {
                b = read();
                checkEof();
            } while (Character.isWhitespace(b));
            StringBuilder sb = new StringBuilder();
            do {
                sb.append(b);
                b = read();
            } while (!eof && !Character.isWhitespace(b));
            return sb.toString();
        }

        int nextInt() {
            return Integer.valueOf(next());
        }

        long nextLong() {
            return Long.valueOf(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }
    }
}
