import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Jenish
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        EMatchingVsIndependentSet solver = new EMatchingVsIndependentSet();
        solver.solve(1, in, out);
        out.close();
    }

    static class EMatchingVsIndependentSet {
        ArrayList<pair>[] arrayList;
        boolean[] visited;

        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int t = in.scanInt();
            while (t-- > 0) {
                int n = in.scanInt();
                int m = in.scanInt();
                arrayList = new ArrayList[3 * n + 1];
                visited = new boolean[3 * n + 1];
                for (int i = 0; i <= 3 * n; i++) arrayList[i] = new ArrayList<>();
                for (int i = 0; i < m; i++) {
                    int u = in.scanInt();
                    int v = in.scanInt();
                    arrayList[u].add(new pair(v, i));
                    arrayList[v].add(new pair(u, i));
                }
                ArrayList<Integer> mat = new ArrayList<>();
                for (int i = 1; i <= 3 * n; i++) {
                    if (visited[i]) continue;
                    for (pair yy : arrayList[i]) {
                        int y = yy.v;
                        if (visited[y]) continue;
                        mat.add(yy.index);
                        visited[i] = visited[y] = true;
                        break;
                    }
                }

                if (mat.size() >= n) {
                    out.println("Matching");
                    for (int i = 0, j = 0; i < mat.size() && j < n; i++, j++) out.print((mat.get(i) + 1) + " ");
                    out.println();
                } else {
                    out.println("IndSet");
                    for (int i = 1, j = 0; i <= 3 * n && j < n; i++)
                        if (!visited[i]) {
                            out.print(i + " ");
                            j++;
                        }
                    out.println();
                }


            }
        }

        class pair {
            int v;
            int index;

            public pair(int v, int index) {
                this.v = v;
                this.index = index;
            }

        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int INDEX;
        private BufferedInputStream in;
        private int TOTAL;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (INDEX >= TOTAL) {
                INDEX = 0;
                try {
                    TOTAL = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (TOTAL <= 0) return -1;
            }
            return buf[INDEX++];
        }

        public int scanInt() {
            int I = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    I *= 10;
                    I += n - '0';
                    n = scan();
                }
            }
            return neg * I;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
            else return false;
        }

    }
}

