You are given a graph with $3 \cdot n$ vertices and $m$ edges. You are to find a matching of $n$ edges, or an independent set of $n$ vertices.

A set of edges is called a matching if no two edges share an endpoint.

A set of vertices is called an independent set if no two vertices are connected with an edge.


-----Input-----

The first line contains a single integer $T \ge 1$ — the number of graphs you need to process. The description of $T$ graphs follows.

The first line of description of a single graph contains two integers $n$ and $m$, where $3 \cdot n$ is the number of vertices, and $m$ is the number of edges in the graph ($1 \leq n \leq 10^{5}$, $0 \leq m \leq 5 \cdot 10^{5}$).

Each of the next $m$ lines contains two integers $v_i$ and $u_i$ ($1 \leq v_i, u_i \leq 3 \cdot n$), meaning that there is an edge between vertices $v_i$ and $u_i$.

It is guaranteed that there are no self-loops and no multiple edges in the graph.

It is guaranteed that the sum of all $n$ over all graphs in a single test does not exceed $10^{5}$, and the sum of all $m$ over all graphs in a single test does not exceed $5 \cdot 10^{5}$.


-----Output-----

Print your answer for each of the $T$ graphs. Output your answer for a single graph in the following format.

If you found a matching of size $n$, on the first line print "Matching" (without quotes), and on the second line print $n$ integers — the indices of the edges in the matching. The edges are numbered from $1$ to $m$ in the input order.

If you found an independent set of size $n$, on the first line print "IndSet" (without quotes), and on the second line print $n$ integers — the indices of the vertices in the independent set.

If there is no matching and no independent set of the specified size, print "Impossible" (without quotes).

You can print edges and vertices in any order.

If there are several solutions, print any. In particular, if there are both a matching of size $n$, and an independent set of size $n$, then you should print exactly one of such matchings or exactly one of such independent sets.


-----Example-----
Input
4
1 2
1 3
1 2
1 2
1 3
1 2
2 5
1 2
3 1
1 4
5 1
1 6
2 15
1 2
1 3
1 4
1 5
1 6
2 3
2 4
2 5
2 6
3 4
3 5
3 6
4 5
4 6
5 6

Output
Matching
2
IndSet
1
IndSet
2 4
Matching
1 15



-----Note-----

The first two graphs are same, and there are both a matching of size 1 and an independent set of size 1. Any of these matchings and independent sets is a correct answer.

The third graph does not have a matching of size 2, however, there is an independent set of size 2. Moreover, there is an independent set of size 5: 2 3 4 5 6. However such answer is not correct, because you are asked to find an independent set (or matching) of size exactly $n$.

The fourth graph does not have an independent set of size 2, but there is a matching of size 2.

Source: codeforces | Difficulty: HARD
Tags: Greedy algorithms

Sorting

Graph algorithms

Constructive algorithms


Solutions:
import sys

def main():
	it = iter(map(int, sys.stdin.read().split()))
	t = next(it)
	for _ in range(t):
		n = next(it)
		m = next(it)
		total_node = 3 * n
		is_node_covered = [False for _ in range(total_node + 1)]
		is_edge_in_matching = [False for _ in range(m + 1)]
		matching_edge_count = 0
		for i in range(1, m + 1):
			u = next(it)
			v = next(it)
			if not is_node_covered[u] and (not is_node_covered[v]):
				is_node_covered[u] = is_node_covered[v] = True
				is_edge_in_matching[i] = True
				matching_edge_count += 1
		ansL = []
		if matching_edge_count >= n:
			ansL.append('Matching\n')
			edge_taken = 0
			for i in range(1, m + 1):
				if is_edge_in_matching[i]:
					ansL.append(str(i) + ' ')
					edge_taken += 1
					if edge_taken == n:
						break
		else:
			ansL.append('IndSet\n')
			node_taken = 0
			for i in range(1, total_node + 1):
				if not is_node_covered[i]:
					ansL.append(str(i) + ' ')
					node_taken += 1
					if node_taken == n:
						break
		ansL.append('\n')
		sys.stdout.write(''.join(ansL))

def __starting_point():
	main()
__starting_point()


from sys import stdin
input = stdin.readline

def solve_graph():
	(n, m) = map(int, input().split())
	included = [False] + [True] * (3 * n)
	matching = []
	for i in range(1, m + 1):
		(e1, e2) = map(int, input().split())
		if included[e1] and included[e2]:
			matching.append(i)
			included[e1] = False
			included[e2] = False
	if len(matching) >= n:
		print('Matching')
		print(*matching[:n])
		return
	intset = [x for (x, b) in enumerate(included) if b]
	print('IndSet')
	print(*list(intset)[:n])
t = int(input())
for _ in range(t):
	solve_graph()


import sys
input = sys.stdin.readline
T = int(input())
ver = set()
for _ in range(T):
	ver.clear()
	(n, m) = map(int, input().split())
	n *= 3
	edge = []
	for __ in range(m):
		(u, v) = map(int, input().split())
		if u not in ver and v not in ver:
			edge.append(__ + 1)
			ver.add(u)
			ver.add(v)
			if len(edge) == n // 3:
				print('Matching')
				print(*edge[:n // 3])
				for x in range(__ + 1, m):
					input()
				break
	if len(edge) < n // 3:
		asd = []
		for x in range(1, n + 1):
			if x not in ver:
				asd.append(x)
			if len(asd) == n // 3:
				print('IndSet')
				print(*asd[:n // 3])
				break
		if len(asd) < n // 3:
			print('Impossible')


import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
	(n, m) = map(int, input().split())
	v = set(range(1, 3 * n + 1))
	e = []
	for i in range(1, m + 1):
		(a, b) = map(int, input().split())
		if a in v and b in v:
			e.append(i)
			v.remove(a)
			v.remove(b)
	if len(e) >= n:
		print('Matching')
		print(*e[:n])
	else:
		print('IndSet')
		print(*list(v)[:n])


def main():
	T = int(input())
	v_cover = set()
	for _ in range(T):
		(n, m) = map(int, input().split())
		v_count = 3 * n
		v_cover.clear()
		i_cover = []
		for k in range(m):
			edge = list(map(int, input().split()))
			if edge[0] not in v_cover and edge[1] not in v_cover:
				v_cover.add(edge[0])
				v_cover.add(edge[1])
				i_cover.append(k + 1)
				if len(i_cover) == n:
					print('Matching')
					print(*i_cover[:n])
					for _ in range(k + 1, m):
						input()
					break
		if len(i_cover) < n:
			v_independent = []
			for vert in range(1, 3 * n + 1):
				if vert not in v_cover:
					v_independent.append(vert)
				if len(v_independent) == n:
					print('IndSet')
					print(*v_independent)
					break
			if len(v_independent) < n:
				print('Impossible')
import sys
input = sys.stdin.readline
main()


from sys import stdin
input = stdin.readline
T = int(input())
for _ in range(T):
	(n, m) = [int(i) for i in input().split()]
	ind_edg_v = [True] * (3 * n + 1)
	ind_edg_e = [0] * n
	num_edg = 0
	for j in range(m):
		(edge_0, edge_1) = [int(i) for i in input().split()]
		if num_edg < n:
			if ind_edg_v[edge_0] and ind_edg_v[edge_1]:
				ind_edg_e[num_edg] = j + 1
				(ind_edg_v[edge_0], ind_edg_v[edge_1]) = (False, False)
				num_edg += 1
	if num_edg == n:
		print('Matching')
		print(' '.join([str(i) for i in ind_edg_e]))
	else:
		print('IndSet')
		vertex = 0
		for i in range(n):
			vertex += 1
			while not ind_edg_v[vertex]:
				vertex += 1
			print(vertex, end=' ')
		print()


import sys
input = sys.stdin.readline
sys.setrecursionlimit(100000)

def getN():
	return int(input())

def getList():
	return list(map(int, input().split()))
import math

def prmatch(ans):
	print('Matching')
	print(*ans)

def solve():
	(n, m) = getList()
	vertexes = [[] for i in range(3 * n)]
	used = [0 for i in range(3 * n)]
	ans = []
	lans = 0
	for i in range(m):
		(a, b) = getList()
		if used[a - 1] == 0 and used[b - 1] == 0:
			ans.append(i + 1)
			lans += 1
			if lans == n:
				prmatch(ans)
				for rem in range(m - i - 1):
					_ = input()
				return
			used[a - 1] = 1
			used[b - 1] = 1
	indset = []
	for (i, u) in enumerate(used):
		if u == 0:
			indset.append(i + 1)
	print('IndSet')
	print(*indset[:n])
	return
t = getN()
for times in range(t):
	solve()


import os
import sys
import math
from io import BytesIO, IOBase
import io
from fractions import Fraction
import collections
from itertools import permutations
from collections import defaultdict
from collections import deque
from collections import Counter
import threading
BUFSIZE = 8192

class FastIO(IOBase):
	newlines = 0

	def __init__(self, file):
		self._fd = file.fileno()
		self.buffer = BytesIO()
		self.writable = 'x' in file.mode or 'r' not in file.mode
		self.write = self.buffer.write if self.writable else None

	def read(self):
		while True:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			if not b:
				break
			ptr = self.buffer.tell()
			(self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr))
		self.newlines = 0
		return self.buffer.read()

	def readline(self):
		while self.newlines == 0:
			b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
			self.newlines = b.count(b'\n') + (not b)
			ptr = self.buffer.tell()
			(self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr))
		self.newlines -= 1
		return self.buffer.readline()

	def flush(self):
		if self.writable:
			os.write(self._fd, self.buffer.getvalue())
			(self.buffer.truncate(0), self.buffer.seek(0))

class IOWrapper(IOBase):

	def __init__(self, file):
		self.buffer = FastIO(file)
		self.flush = self.buffer.flush
		self.writable = self.buffer.writable
		self.write = lambda s: self.buffer.write(s.encode('ascii'))
		self.read = lambda : self.buffer.read().decode('ascii')
		self.readline = lambda : self.buffer.readline().decode('ascii')
(sys.stdin, sys.stdout) = (IOWrapper(sys.stdin), IOWrapper(sys.stdout))
input = lambda : sys.stdin.readline().rstrip('\r\n')

class SegmentTree:

	def __init__(self, data, default=0, func=lambda a, b: max(a, b)):
		self._default = default
		self._func = func
		self._len = len(data)
		self._size = _size = 1 << (self._len - 1).bit_length()
		self.data = [default] * (2 * _size)
		self.data[_size:_size + self._len] = data
		for i in reversed(range(_size)):
			self.data[i] = func(self.data[i + i], self.data[i + i + 1])

	def __delitem__(self, idx):
		self[idx] = self._default

	def __getitem__(self, idx):
		return self.data[idx + self._size]

	def __setitem__(self, idx, value):
		idx += self._size
		self.data[idx] = value
		idx >>= 1
		while idx:
			self.data[idx] = self._func(self.data[2 * idx], self.data[2 * idx + 1])
			idx >>= 1

	def __len__(self):
		return self._len

	def query(self, start, stop):
		if start == stop:
			return self.__getitem__(start)
		stop += 1
		start += self._size
		stop += self._size
		res = self._default
		while start < stop:
			if start & 1:
				res = self._func(res, self.data[start])
				start += 1
			if stop & 1:
				stop -= 1
				res = self._func(res, self.data[stop])
			start >>= 1
			stop >>= 1
		return res

	def __repr__(self):
		return 'SegmentTree({0})'.format(self.data)

class SegmentTree1:

	def __init__(self, data, default=0, func=lambda a, b: a + b):
		self._default = default
		self._func = func
		self._len = len(data)
		self._size = _size = 1 << (self._len - 1).bit_length()
		self.data = [default] * (2 * _size)
		self.data[_size:_size + self._len] = data
		for i in reversed(range(_size)):
			self.data[i] = func(self.data[i + i], self.data[i + i + 1])

	def __delitem__(self, idx):
		self[idx] = self._default

	def __getitem__(self, idx):
		return self.data[idx + self._size]

	def __setitem__(self, idx, value):
		idx += self._size
		self.data[idx] = value
		idx >>= 1
		while idx:
			self.data[idx] = self._func(self.data[2 * idx], self.data[2 * idx + 1])
			idx >>= 1

	def __len__(self):
		return self._len

	def query(self, start, stop):
		if start == stop:
			return self.__getitem__(start)
		stop += 1
		start += self._size
		stop += self._size
		res = self._default
		while start < stop:
			if start & 1:
				res = self._func(res, self.data[start])
				start += 1
			if stop & 1:
				stop -= 1
				res = self._func(res, self.data[stop])
			start >>= 1
			stop >>= 1
		return res

	def __repr__(self):
		return 'SegmentTree({0})'.format(self.data)
MOD = 10 ** 9 + 7

class Factorial:

	def __init__(self, MOD):
		self.MOD = MOD
		self.factorials = [1, 1]
		self.invModulos = [0, 1]
		self.invFactorial_ = [1, 1]

	def calc(self, n):
		if n <= -1:
			print('Invalid argument to calculate n!')
			print('n must be non-negative value. But the argument was ' + str(n))
			exit()
		if n < len(self.factorials):
			return self.factorials[n]
		nextArr = [0] * (n + 1 - len(self.factorials))
		initialI = len(self.factorials)
		prev = self.factorials[-1]
		m = self.MOD
		for i in range(initialI, n + 1):
			prev = nextArr[i - initialI] = prev * i % m
		self.factorials += nextArr
		return self.factorials[n]

	def inv(self, n):
		if n <= -1:
			print('Invalid argument to calculate n^(-1)')
			print('n must be non-negative value. But the argument was ' + str(n))
			exit()
		p = self.MOD
		pi = n % p
		if pi < len(self.invModulos):
			return self.invModulos[pi]
		nextArr = [0] * (n + 1 - len(self.invModulos))
		initialI = len(self.invModulos)
		for i in range(initialI, min(p, n + 1)):
			next = -self.invModulos[p % i] * (p // i) % p
			self.invModulos.append(next)
		return self.invModulos[pi]

	def invFactorial(self, n):
		if n <= -1:
			print('Invalid argument to calculate (n^(-1))!')
			print('n must be non-negative value. But the argument was ' + str(n))
			exit()
		if n < len(self.invFactorial_):
			return self.invFactorial_[n]
		self.inv(n)
		nextArr = [0] * (n + 1 - len(self.invFactorial_))
		initialI = len(self.invFactorial_)
		prev = self.invFactorial_[-1]
		p = self.MOD
		for i in range(initialI, n + 1):
			prev = nextArr[i - initialI] = prev * self.invModulos[i % p] % p
		self.invFactorial_ += nextArr
		return self.invFactorial_[n]

class Combination:

	def __init__(self, MOD):
		self.MOD = MOD
		self.factorial = Factorial(MOD)

	def ncr(self, n, k):
		if k < 0 or n < k:
			return 0
		k = min(k, n - k)
		f = self.factorial
		return f.calc(n) * f.invFactorial(max(n - k, k)) * f.invFactorial(min(k, n - k)) % self.MOD
mod = 10 ** 9 + 7
omod = 998244353
prime = [True for i in range(11)]
prime[0] = prime[1] = False

def SieveOfEratosthenes(n=10):
	p = 2
	c = 0
	while p <= n:
		if prime[p] == True:
			c += 1
			for i in range(p, n + 1, p):
				prime[i] = False
		p += 1

class DSU:

	def __init__(self, R, C):
		self.par = range(R * C + 1)
		self.rnk = [0] * (R * C + 1)
		self.sz = [1] * (R * C + 1)

	def find(self, x):
		if self.par[x] != x:
			self.par[x] = self.find(self.par[x])
		return self.par[x]

	def union(self, x, y):
		(xr, yr) = (self.find(x), self.find(y))
		if xr == yr:
			return
		if self.rnk[xr] < self.rnk[yr]:
			(xr, yr) = (yr, xr)
		if self.rnk[xr] == self.rnk[yr]:
			self.rnk[xr] += 1
		self.par[yr] = xr
		self.sz[xr] += self.sz[yr]

	def size(self, x):
		return self.sz[self.find(x)]

	def top(self):
		return self.size(len(self.sz) - 1) - 1

class LazySegTree:

	def __init__(self, _op, _e, _mapping, _composition, _id, v):

		def set(p, x):
			assert 0 <= p < _n
			p += _size
			for i in range(_log, 0, -1):
				_push(p >> i)
			_d[p] = x
			for i in range(1, _log + 1):
				_update(p >> i)

		def get(p):
			assert 0 <= p < _n
			p += _size
			for i in range(_log, 0, -1):
				_push(p >> i)
			return _d[p]

		def prod(l, r):
			assert 0 <= l <= r <= _n
			if l == r:
				return _e
			l += _size
			r += _size
			for i in range(_log, 0, -1):
				if l >> i << i != l:
					_push(l >> i)
				if r >> i << i != r:
					_push(r >> i)
			sml = _e
			smr = _e
			while l < r:
				if l & 1:
					sml = _op(sml, _d[l])
					l += 1
				if r & 1:
					r -= 1
					smr = _op(_d[r], smr)
				l >>= 1
				r >>= 1
			return _op(sml, smr)

		def apply(l, r, f):
			assert 0 <= l <= r <= _n
			if l == r:
				return
			l += _size
			r += _size
			for i in range(_log, 0, -1):
				if l >> i << i != l:
					_push(l >> i)
				if r >> i << i != r:
					_push(r - 1 >> i)
			l2 = l
			r2 = r
			while l < r:
				if l & 1:
					_all_apply(l, f)
					l += 1
				if r & 1:
					r -= 1
					_all_apply(r, f)
				l >>= 1
				r >>= 1
			l = l2
			r = r2
			for i in range(1, _log + 1):
				if l >> i << i != l:
					_update(l >> i)
				if r >> i << i != r:
					_update(r - 1 >> i)

		def _update(k):
			_d[k] = _op(_d[2 * k], _d[2 * k + 1])

		def _all_apply(k, f):
			_d[k] = _mapping(f, _d[k])
			if k < _size:
				_lz[k] = _composition(f, _lz[k])

		def _push(k):
			_all_apply(2 * k, _lz[k])
			_all_apply(2 * k + 1, _lz[k])
			_lz[k] = _id
		_n = len(v)
		_log = _n.bit_length()
		_size = 1 << _log
		_d = [_e] * (2 * _size)
		_lz = [_id] * _size
		for i in range(_n):
			_d[_size + i] = v[i]
		for i in range(_size - 1, 0, -1):
			_update(i)
		self.set = set
		self.get = get
		self.prod = prod
		self.apply = apply
MIL = 1 << 20

def makeNode(total, count):
	return total * MIL + count

def getTotal(node):
	return math.floor(node / MIL)

def getCount(node):
	return node - getTotal(node) * MIL
nodeIdentity = makeNode(0.0, 0.0)

def nodeOp(node1, node2):
	return node1 + node2
	return makeNode(getTotal(node1) + getTotal(node2), getCount(node1) + getCount(node2))
identityMapping = -1

def mapping(tag, node):
	if tag == identityMapping:
		return node
	count = getCount(node)
	return makeNode(tag * count, count)

def composition(mapping1, mapping2):
	return mapping1 if mapping1 != identityMapping else mapping2

def memodict(f):

	class memodict(dict):

		def __missing__(self, key):
			ret = self[key] = f(key)
			return ret
	return memodict().__getitem__

def pollard_rho(n):
	if n & 1 == 0:
		return 2
	if n % 3 == 0:
		return 3
	s = (n - 1 & 1 - n).bit_length() - 1
	d = n >> s
	for a in [2, 325, 9375, 28178, 450775, 9780504, 1795265022]:
		p = pow(a, d, n)
		if p == 1 or p == n - 1 or a % n == 0:
			continue
		for _ in range(s):
			prev = p
			p = p * p % n
			if p == 1:
				return math.gcd(prev - 1, n)
			if p == n - 1:
				break
		else:
			for i in range(2, n):
				(x, y) = (i, (i * i + 1) % n)
				f = math.gcd(abs(x - y), n)
				while f == 1:
					(x, y) = ((x * x + 1) % n, (y * y + 1) % n)
					y = (y * y + 1) % n
					f = math.gcd(abs(x - y), n)
				if f != n:
					return f
	return n

@memodict
def prime_factors(n):
	if n <= 1:
		return Counter()
	f = pollard_rho(n)
	return Counter([n]) if f == n else prime_factors(f) + prime_factors(n // f)

def distinct_factors(n):
	factors = [1]
	for (p, exp) in prime_factors(n).items():
		factors += [p ** i * factor for factor in factors for i in range(1, exp + 1)]
	return factors

def all_factors(n):
	(small, large) = ([], [])
	for i in range(1, int(n ** 0.5) + 1, 2 if n & 1 else 1):
		if not n % i:
			small.append(i)
			large.append(n // i)
	if small[-1] == large[-1]:
		large.pop()
	large.reverse()
	small.extend(large)
	return small

def binarySearch(arr, n, key):
	left = 0
	right = n - 1
	mid = 0
	res = n
	while left <= right:
		mid = (right + left) // 2
		if arr[mid] > key:
			res = mid
			right = mid - 1
		else:
			left = mid + 1
	return res

def binarySearch1(arr, n, key):
	left = 0
	right = n - 1
	mid = 0
	res = -1
	while left <= right:
		mid = (right + left) // 2
		if arr[mid] > key:
			right = mid - 1
		else:
			res = mid
			left = mid + 1
	return res
t = 1
t = int(input())
for _ in range(t):
	(n, m) = map(int, input().split())
	vertices = set([i for i in range(1, 3 * n + 1)])
	matching = []
	for i in range(m):
		(x, y) = map(int, input().split())
		if x in vertices and y in vertices:
			matching.append(i + 1)
			vertices.remove(x)
			vertices.remove(y)
	if len(matching) >= n:
		print('Matching')
		print(*matching[:n])
	elif len(vertices) >= n:
		print('IndSet')
		a = list(vertices)
		print(*a[:n])
	else:
		print('Impossible')


import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
	(N, M) = list(map(int, input().split()))
	X = [[] for i in range(3 * N)]
	for i in range(M):
		(x, y) = list(map(int, input().split()))
		(x, y) = (min(x, y), max(x, y))
		X[x - 1].append((y - 1, i + 1))
	MAT = []
	IND = []
	DONE = [0] * 3 * N
	for i in range(3 * N):
		if DONE[i]:
			continue
		for (j, ind) in X[i]:
			if DONE[j] == 0:
				MAT.append(ind)
				DONE[i] = 1
				DONE[j] = 1
				break
		else:
			IND.append(i + 1)
	if len(MAT) >= N:
		print('Matching')
		print(*MAT[:N])
	else:
		print('IndSet')
		print(*IND[:N])


import sys
input = sys.stdin.readline
maxn = 100005
hell = 1000000007
vis = [0] * 3 * maxn

def meowmeow321():
	(n, m) = map(int, input().split())
	for i in range(3 * n + 1):
		vis[i] = 0
	elst = []
	for i in range(m):
		(x, y) = map(int, input().split())
		if not vis[x] and (not vis[y]):
			vis[x] = 1
			vis[y] = 1
			elst.append(i + 1)
	if len(elst) >= n:
		print('Matching')
		for i in range(n):
			print(elst[i], end=' ')
		print('')
	else:
		print('IndSet')
		cnt = 0
		cur = 1
		while cnt < n and cur <= 3 * n:
			if not vis[cur]:
				print(cur, end=' ')
				cnt += 1
			cur += 1
		print('')
t = int(input())
for xxx in range(t):
	meowmeow321()


import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
	(n, m) = map(int, input().split())
	edges = [0] * m
	for i in range(m):
		edges[i] = tuple(map(int, input().split()))
	used = [0] * (3 * n)
	edgess = []
	check = 0
	for i in range(m):
		if used[edges[i][0] - 1] == used[edges[i][1] - 1] == 0:
			edgess.append(i + 1)
			used[edges[i][0] - 1] = 1
			used[edges[i][1] - 1] = 1
			check += 1
	if check >= n:
		useful = edgess[:n]
		edgess = [str(guy) for guy in useful]
		print('Matching')
		print(' '.join(edgess))
	else:
		indep = []
		for i in range(1, 3 * n + 1):
			if used[i - 1] == 0:
				indep.append(i)
		useful = indep[:n]
		verts = [str(guy) for guy in useful]
		print('IndSet')
		print(' '.join(verts))


from sys import stdin
input = stdin.readline
q = int(input())
for query in range(q):
	(n, m) = map(int, input().split())
	dupa = [0] * (3 * n + 1)
	edges = []
	for i in range(m):
		(u, v) = map(int, input().split())
		if dupa[u] == 0 and dupa[v] == 0:
			dupa[u] = 1
			dupa[v] = 1
			if len(edges) < n:
				edges.append(i + 1)
	if len(edges) == n:
		print('Matching')
		print(*edges)
	else:
		print('IndSet')
		chuj = 0
		for i in range(1, 3 * n + 1):
			if chuj == n:
				break
			if dupa[i] == 0:
				if chuj < n - 1:
					print(i, end=' ')
				else:
					print(i)
				chuj += 1


import sys
input = sys.stdin.readline
T = int(input())
for testcases in range(T):
	(n, m) = map(int, input().split())
	EDGE = [[0, 0]] + [list(map(int, input().split())) for i in range(m)]
	USED = [0] * (3 * n + 1)
	count = 0
	ANS = []
	for i in range(1, m + 1):
		(x, y) = EDGE[i]
		if USED[x] == 0 and USED[y] == 0:
			count += 1
			ANS.append(i)
			USED[x] = 1
			USED[y] = 1
			if count == n:
				print('Matching')
				print(*ANS)
				break
	else:
		ANS = []
		count = 0
		for i in range(1, 3 * n + 1):
			if USED[i] == 0:
				count += 1
				ANS.append(i)
				if count == n:
					print('IndSet')
					print(*ANS)
					break


import sys
input = sys.stdin.readline

def main():
	tes = int(input())
	for testcase in [0] * tes:
		(n, m) = map(int, input().split())
		new = [True] * (3 * n)
		res = []
		for i in range(1, m + 1):
			(u, v) = map(int, input().split())
			if new[u - 1] and new[v - 1]:
				if len(res) < n:
					res.append(i)
					new[u - 1] = new[v - 1] = False
		if len(res) >= n:
			print('Matching')
			print(*res)
		else:
			vs = []
			for i in range(3 * n):
				if new[i]:
					vs.append(i + 1)
					if len(vs) >= n:
						break
			print('IndSet')
			print(*vs)
main()


import sys
import io, os
input = io.BytesIO(os.read(0, os.fstat(0).st_size)).readline
t = int(input())
for _ in range(t):
	(n, m) = map(int, input().split())
	edge = []
	for i in range(m):
		(u, v) = map(int, input().split())
		(u, v) = (u - 1, v - 1)
		edge.append((u, v))
	used = set()
	M = set()
	for (i, (u, v)) in enumerate(edge):
		if u not in used and v not in used:
			M.add(i + 1)
			used.add(u)
			used.add(v)
	if len(M) >= n:
		M = list(M)
		M = M[0:n]
		print('Matching')
		print(*M)
		continue
	S = []
	for i in range(3 * n):
		if i not in used:
			S.append(i + 1)
			if len(S) == n:
				break
	if len(S) == n:
		print('IndSet')
		print(*S)
		continue
	print('Impossible')


def naiveSolve(n):
	return

def main():
	t = int(input())
	allans = []
	for _ in range(t):
		(n, m) = readIntArr()
		edges = []
		for _ in range(m):
			(u, v) = readIntArr()
			edges.append([u, v])
		visited = [False for _ in range(3 * n + 1)]
		matching = []
		for (i, [u, v]) in enumerate(edges):
			if visited[u] == False and visited[v] == False:
				matching.append(i + 1)
				visited[u] = visited[v] = True
		if len(matching) >= n:
			allans.append(['Matching'])
			allans.append(matching[:n])
		else:
			ind = []
			for i in range(1, 3 * n + 1):
				if visited[i] == False:
					ind.append(i)
					if len(ind) == n:
						break
			allans.append(['IndSet'])
			allans.append(ind)
	multiLineArrayOfArraysPrint(allans)
	return
import sys
input = sys.stdin.buffer.readline

def oneLineArrayPrint(arr):
	print(' '.join([str(x) for x in arr]))

def multiLineArrayPrint(arr):
	print('\n'.join([str(x) for x in arr]))

def multiLineArrayOfArraysPrint(arr):
	print('\n'.join([' '.join([str(x) for x in y]) for y in arr]))

def readIntArr():
	return [int(x) for x in input().split()]

def makeArr(defaultValFactory, dimensionArr):
	dv = defaultValFactory
	da = dimensionArr
	if len(da) == 1:
		return [dv() for _ in range(da[0])]
	else:
		return [makeArr(dv, da[1:]) for _ in range(da[0])]

def queryInteractive(l, r):
	print('? {} {}'.format(l, r))
	sys.stdout.flush()
	return int(input())

def answerInteractive(x):
	print('! {}'.format(x))
	sys.stdout.flush()
inf = float('inf')
MOD = 10 ** 9 + 7
from math import gcd, floor, ceil
for _abc in range(1):
	main()


import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
	(n, m) = map(int, input().split())
	v = [True] * (3 * n + 1)
	e = [0] * n
	ptr = 0
	for i in range(1, m + 1):
		(a, b) = map(int, input().split())
		if ptr < n and v[a] and v[b]:
			e[ptr] = i
			ptr += 1
			v[a] = False
			v[b] = False
	if ptr == n:
		print('Matching')
		print(*e)
	else:
		print('IndSet')
		cnt = 0
		for i in range(1, n * 3 + 1):
			if v[i]:
				print(i, end=' ')
				cnt += 1
			if cnt == n:
				print()
				break


from sys import stdin
from sys import setrecursionlimit as SRL
SRL(10 ** 7)
rd = stdin.readline
rrd = lambda : map(int, rd().strip().split())
t = int(input())
while t:
	(n, m) = map(int, rd().split())
	out = [0] * (3 * n + 1)
	mans = []
	nans = []
	for i in range(1, m + 1):
		(u, v) = map(int, rd().split())
		if not out[u] and (not out[v]):
			out[u] = out[v] = 1
			mans.append(i)
	if len(mans) >= n:
		print('Matching')
		print(*mans[:n])
	else:
		print('IndSet')
		for i in range(1, 1 + 3 * n):
			if not out[i]:
				nans.append(i)
			if len(nans) >= n:
				break
		print(*nans)
	t -= 1


from sys import stdin
input = stdin.readline
t = int(input())
for k in range(t):
	(n, m) = map(int, input().split(' '))
	a = [i for i in range(1, n + 1)]
	qq = set(range(1, 3 * n + 1))
	e = []
	for i in range(1, m + 1):
		(a1, a2) = map(int, input().split(' '))
		if a1 in qq and a2 in qq:
			e.append(i)
			qq.remove(a1)
			qq.remove(a2)
	if len(qq) >= n:
		print('IndSet')
		print(*list(qq)[:n])
	else:
		print('Matching')
		print(*e[:n])