#include <bits/stdc++.h>
bool local = false;
using namespace std;
template <class T>
string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T>
void print(T v) {
  cout << ((int)(v).size()) << "\n";
  for (auto x : v) cout << x << ' ';
  cout << "\n";
};
template <class T>
void print1(T v) {
  cout << ((int)(v).size()) << "\n";
  for (auto x : v) cout << x + 1 << ' ';
  cout << "\n";
};
template <class T1, class T2>
ostream &operator<<(ostream &o, pair<T1, T2> x) {
  return o << x.first << ' ' << x.second;
}
template <class T1, class T2>
istream &operator>>(istream &o, pair<T1, T2> &x) {
  return o >> x.first >> x.second;
}
template <class T1, class T2>
pair<T1, T2> operator+(pair<T1, T2> a, pair<T1, T2> b) {
  a.first += b.first;
  a.second += b.second;
  return a;
}
template <class T1, class T2>
pair<T1, T2> operator-(pair<T1, T2> a, pair<T1, T2> b) {
  a.first -= b.first;
  a.second -= b.second;
  return a;
}
template <class T1, class T2>
void operator+=(pair<T1, T2> &a, pair<T1, T2> b) {
  a.first += b.first;
  a.second += b.second;
}
template <class T1, class T2>
void operator-=(pair<T1, T2> &a, pair<T1, T2> b) {
  a.first -= b.first;
  a.second -= b.second;
}
int nint() {
  int x;
  cin >> x;
  return x;
}
double getTime() { return clock() / (double)CLOCKS_PER_SEC; };
mt19937 rnd(0);
int rand(int n) { return rnd() % n; }
int rand(int l, int r) { return rnd() % (r - l + 1) + l; }
const int mod = 1000000000 + 7;
void initIO() {
  if (local) {
    freopen("input.txt", "r", stdin);
    srand((int)time(0));
    rnd.seed((int)time(0));
  } else {
  }
  {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
  };
}
void solve();
int main() {
  initIO();
  int tc = 1;
  cin >> tc;
  for (int tt = 0; tt < (tc); tt++) {
    solve();
  }
  if (local)
    cout << "\n"
         << "time = " << getTime() << "\n";
}
int n;
int m;
int was[300500];
void solve() {
  cin >> n >> m;
  n *= 3;
  for (int i = 0; i < (n); i++) was[i] = 0;
  vector<int> v;
  for (int i = 0; i < (m); i++) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    if (was[a] || was[b]) continue;
    was[a] = was[b] = 1;
    v.emplace_back(i + 1);
  }
  if (((int)(v).size()) >= n / 3) {
    cout << "Matching"
         << "\n";
    for (int i = 0; i < (n / 3); i++) cout << v[i] << ' ';
    cout << "\n";
  } else {
    cout << "IndSet"
         << "\n";
    vector<int> v;
    for (int i = 0; i < (n); i++)
      if (!was[i]) v.emplace_back(i + 1);
    for (int i = 0; i < (n / 3); i++) cout << v[i] << ' ';
    cout << "\n";
  }
}
