/**
 * BaZ :D
 */

import java.util.*;
import java.io.*;
import static java.lang.Math.*;

public class ACMIND
{
    static FastReader scan;
    static PrintWriter pw;
    static long MOD = 1_000_000_007;
    static long INF = 1_000_000_000_000_000_000L;
    static long inf = 2_000_000_000;
    public static void main(String[] args) {
        new Thread(null,null,"BaZ",1<<25)
        {
            public void run()
            {
                try
                {
                    solve();
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                    System.exit(1);
                }
            }
        }.start();
    }

    static void solve() throws IOException
    {
        scan = new FastReader();
        pw = new PrintWriter(System.out,true);
        StringBuilder sb = new StringBuilder();
        int t = ni();
        while(t-->0) {
            int n = ni(), m = ni();
            TreeSet<Tuple> set = new TreeSet<>();
            ArrayList<Pair> adj[] = new ArrayList[3*n+1];
            for(int i=1;i<=3*n;++i) {
                adj[i] = new ArrayList<>();
            }
            for(int i=0;i<m;++i) {
                int u = ni(), v = ni();
                int U = min(u,v);
                int V = max(u,v);
                set.add(new Tuple(U,V, i));
                adj[U].add(new Pair(V,i));
                adj[V].add(new Pair(U, i));
            }
            TreeSet<Tuple> qualified = new TreeSet<>();
            while(!set.isEmpty()) {
                Tuple e = set.pollFirst();
                qualified.add(e);
                //pl("Adding "+e+" to qualified.");
                for(Pair p : adj[e.x]) {
                    set.remove(new Tuple(min(e.x, p.x), max(e.x, p.x), p.y));
                    //pl("Removed "+new Tuple(e.x, p.x, p.y)+" from candidate edges");
                }
                for(Pair p : adj[e.y]) {
                    set.remove(new Tuple(min(e.y, p.x), max(e.y, p.x), p.y));
                    //pl("Removed "+new Tuple(e.y, p.x, p.y)+" from candidate edges");
                }
            }
            if(qualified.size()>=n) {
                while(qualified.size()>n) {
                    qualified.pollFirst();
                }
                sb.append("Matching\n");
                for(Tuple e : qualified) {
                    sb.append((e.idx+1));
                    sb.append(" ");
                }
                sb.append("\n");
            }
            else {
                boolean good[] = new boolean[3*n+1];
                Arrays.fill(good, true);
                for(Tuple e : qualified) {
                    good[e.x] = good[e.y] = false;
                }
                sb.append("IndSet\n");
                int cnt = 0;
                for(int i=1;i<=3*n;++i) {
                    if(good[i]) {
                        sb.append(i);
                        sb.append(" ");
                        cnt++;
                        if(cnt==n) {
                            break;
                        }
                    }
                }
                sb.append("\n");
            }
        }
        pl(sb);
        pw.flush();
        pw.close();
    }
    static class Pair {
        int x,y;
        Pair(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }
    static class Tuple implements Comparable<Tuple>
    {
        int x,y,idx;
        Tuple(int x,int y, int idx)
        {
            this.x=x;
            this.y=y;
            this.idx = idx;
        }
        public int compareTo(Tuple other)
        {
            if(this.x!=other.x)
                return this.x-other.x;
            return this.y-other.y;
        }
        public String toString()
        {
            return "("+x+","+y+","+idx+")";
        }
    }
    static int ni() throws IOException
    {
        return scan.nextInt();
    }
    static long nl() throws IOException
    {
        return scan.nextLong();
    }
    static double nd() throws IOException
    {
        return scan.nextDouble();
    }
    static void pl()
    {
        pw.println();
    }
    static void p(Object o)
    {
        pw.print(o+" ");
    }
    static void pl(Object o)
    {
        pw.println(o);
    }
    static void psb(StringBuilder sb)
    {
        pw.print(sb);
    }
    static void pa(String arrayName, Object arr[])
    {
        pl(arrayName+" : ");
        for(Object o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, int arr[])
    {
        pl(arrayName+" : ");
        for(int o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, long arr[])
    {
        pl(arrayName+" : ");
        for(long o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, double arr[])
    {
        pl(arrayName+" : ");
        for(double o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, char arr[])
    {
        pl(arrayName+" : ");
        for(char o : arr)
            p(o);
        pl();
    }
    static void pa(String listName, List list)
    {
        pl(listName+" : ");
        for(Object o : list)
            p(o);
        pl();
    }
    static void pa(String arrayName, Object[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(Object o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, int[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(int o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, long[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(long o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, char[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(char o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, double[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(double o : arr[i])
                p(o);
            pl();
        }
    }
    static class FastReader {
        final private int BUFFER_SIZE = 1 << 16;
        private DataInputStream din;
        private byte[] buffer;
        private int bufferPointer, bytesRead;

        public FastReader() {
            din = new DataInputStream(System.in);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        public FastReader(String file_name) throws IOException {
            din = new DataInputStream(new FileInputStream(file_name));
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        public String readLine() throws IOException {
            byte[] buf = new byte[1000000];
            int cnt = 0, c;
            while ((c = read()) != -1) {
                if (c == '\n') break;
                buf[cnt++] = (byte) c;
            }
            return new String(buf, 0, cnt);
        }

        public int nextInt() throws IOException {
            int ret = 0;
            byte c = read();
            while (c <= ' ') c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');
            if (neg) return -ret;
            return ret;
        }

        public long nextLong() throws IOException {
            long ret = 0;
            byte c = read();
            while (c <= ' ') c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');
            if (neg) return -ret;
            return ret;
        }

        public double nextDouble() throws IOException {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ') c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');
            if (c == '.') while ((c = read()) >= '0' && c <= '9') ret += (c - '0') / (div *= 10);
            if (neg) return -ret;
            return ret;
        }

        private void fillBuffer() throws IOException {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1) buffer[0] = -1;
        }

        private byte read() throws IOException {
            if (bufferPointer == bytesRead) fillBuffer();
            return buffer[bufferPointer++];
        }

        public void close() throws IOException {
            if (din == null) return;
            din.close();
        }
    }
}