import java.io.*;
import java.util.*;

public class E implements Runnable {
	public static void main (String[] args) {new Thread(null, new E(), "_cf", 1 << 28).start();}

	int[] deg;
	ArrayList<Edge>[] adj;
	Edge[] list;
	
	public void run() {
		FastScanner fs = new FastScanner();
		PrintWriter out = new PrintWriter(System.out);
		System.err.println("");

		int T = fs.nextInt();
		while(T-->0) {
			int n = fs.nextInt()*3;
			int m = fs.nextInt();
			int g = n/3;
			deg = new int[n];
			list = new Edge[m];
			adj = new ArrayList[n];
			for(int i = 0; i < n; i++) adj[i] = new ArrayList<>();
			
			for(int i = 0; i < m; i++) {
				int u = fs.nextInt()-1, v = fs.nextInt()-1;
				adj[u].add(new Edge(u, v, i));
				adj[v].add(new Edge(v, u, i));
				list[i] = new Edge(u, v, i);
				deg[u]++; deg[v]++;
			}
		
			int[] match = new int[g];
			int ptr = 0;
			
			boolean[] done = new boolean[n];
			Arrays.sort(list);
			for(int i = 0; i < m && ptr < g; i++) {
				Edge now = list[i];
				if(done[now.u] || done[now.v]) continue;
				done[now.u] = done[now.v] = true;
				match[ptr++] = list[i].id+1;
			}
			
			if(ptr == g) {
				out.println("Matching");
				for(int i = 0; i < g; i++) {
					if(i > 0) out.print(" ");
					out.print(match[i]);
				}
				out.println();
				continue;
			}
			
			int[] set = new int[g];
			ptr = 0;
			for(int i = 0; i < n && ptr < g; i++) {
				if(!done[i]) {
					set[ptr++] = i+1;
				}
			}
		
			if(ptr == g) {
				out.println("IndSet");
				for(int i = 0; i < g; i++) {
					if(i > 0) out.print(" ");
					out.print(set[i]);
				}
				out.println();
			}
			
		}
		
		out.close();
	}
	
	class Node implements Comparable<Node> {
		int id, deg;
		Node(int a, int b) {
			id = a; deg = b;
		}
		public int compareTo(Node n) {
			int c = Integer.compare(deg, n.deg);
			if(c == 0) c = Integer.compare(id, n.id);
			return c;
		}
	}
	
	class Edge implements Comparable<Edge> {
		int id, u, v;
		Edge(int a, int b, int i) {
			u = a; v = b;
			id = i;
		}
		public int compareTo(Edge e) {
			return Integer.compare(deg[u]+deg[v], deg[e.u]+deg[e.v]);
		}
	}
	
	class FastScanner {
		public int BS = 1<<16;
		public char NC = (char)0;
		byte[] buf = new byte[BS];
		int bId = 0, size = 0;
		char c = NC;
		double num = 1;
		BufferedInputStream in;

		public FastScanner() {
			in = new BufferedInputStream(System.in, BS);
		}

		public FastScanner(String s) {
			try {
				in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
			}
			catch (Exception e) {
				in = new BufferedInputStream(System.in, BS);
			}
		}

		public char nextChar(){
			while(bId==size) {
				try {
					size = in.read(buf);
				}catch(Exception e) {
					return NC;
				}                
				if(size==-1)return NC;
				bId=0;
			}
			return (char)buf[bId++];
		}

		public int nextInt() {
			return (int)nextLong();
		}

		public long nextLong() {
			num=1;
			boolean neg = false;
			if(c==NC)c=nextChar();
			for(;(c<'0' || c>'9'); c = nextChar()) {
				if(c=='-')neg=true;
			}
			long res = 0;
			for(; c>='0' && c <='9'; c=nextChar()) {
				res = (res<<3)+(res<<1)+c-'0';
				num*=10;
			}
			return neg?-res:res;
		}

		public double nextDouble() {
			double cur = nextLong();
			return c!='.' ? cur:cur+nextLong()/num;
		}

		public String next() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c>32) {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public String nextLine() {
			StringBuilder res = new StringBuilder();
			while(c<=32)c=nextChar();
			while(c!='\n') {
				res.append(c);
				c=nextChar();
			}
			return res.toString();
		}

		public boolean hasNext() {
			if(c>32)return true;
			while(true) {
				c=nextChar();
				if(c==NC)return false;
				else if(c>32)return true;
			}
		}
		
		public int[] nextIntArray(int n) {
			int[] res = new int[n];
			for(int i = 0; i < n; i++) res[i] = nextInt();
			return res;
		}
		
	}

}