#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline bool uax(T &x, T y) {
  return (y > x) ? x = y, true : false;
}
template <typename T>
inline bool uin(T &x, T y) {
  return (y < x) ? x = y, true : false;
}
string to_string(char c) { return "'" + string(1, c) + "'"; }
string to_string(string s) { return '"' + s + '"'; }
string to_string(const char *s) { return to_string((string)s); }
template <typename A>
string to_string(A);
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ": " + to_string(p.second) + ")";
}
template <typename A>
string to_string(A v) {
  bool f = false;
  string r = "{";
  for (auto x : v) {
    if (f) r += ", ";
    r += to_string(x);
    f = true;
  }
  return r += "}";
}
template <typename A>
string to_string(vector<vector<A>> v) {
  string r;
  for (auto x : v) r += "\n" + to_string(x);
  return r;
}
void err(istream_iterator<string>) { cerr << endl; }
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " =: " << to_string(a) << "; ";
  err(++it, args...);
}
template <typename T>
void orz(T ans) {
  cout << ans << endl;
  exit(0);
}
int const MOD = 1e9 + 7;
long long const INF = 1e18;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int tt;
  cin >> tt;
  while (tt--) {
    int n, m;
    cin >> n >> m;
    vector<vector<int>> g(3 * n);
    map<pair<int, int>, int> eid;
    for (int i = 0; i < m; ++i) {
      int u, v;
      cin >> u >> v;
      --u;
      --v;
      g[u].push_back(v);
      g[v].push_back(u);
      eid[{u, v}] = eid[{v, u}] = i;
    }
    vector<bool> mark(3 * n);
    vector<int> edges;
    for (int u = 0; u < 3 * n && int((edges).size()) < n; ++u)
      if (!mark[u]) {
        for (const int &v : g[u])
          if (!mark[v]) {
            mark[u] = mark[v] = true;
            edges.push_back(eid[{u, v}]);
            break;
          }
      }
    if (int((edges).size()) == n) {
      cout << "Matching\n";
      for (int i : edges) cout << i + 1 << " ";
      cout << "\n";
    } else {
      cout << "IndSet\n";
      for (int u = 0, cnt = 0; cnt < n; ++u) {
        if (!mark[u]) {
          cout << u + 1 << " ";
          ++cnt;
        }
      }
      cout << "\n";
    }
  }
  return 0;
}
