#include<bits/stdc++.h> usingnamespace std; #define ll long long constint INF = 0x3f3f3f3f; constint N = 5e5 + 10; int T, n, m; int vis[N]; vector<int>vc; typedef pair<int, int>pii; pii e[N]; intmain(){ scanf("%d", &T); while (T--) { scanf("%d%d", &n, &m); fill(vis, vis + 3 * n + 1, 0); vc.clear(); for (int i = 1; i <= m; i++) { scanf("%d%d", &e[i].first, &e[i].second); } for (int i = 1; i <= m; i++) { if (!vis[e[i].first] && !vis[e[i].second]) { vis[e[i].first] = vis[e[i].second] = 1; vc.push_back(i); } } if ((int)vc.size() >= n) { puts("Matching"); for (int i = 0; i < n; i++)printf("%d%c", vc[i], " \n"[i == n - 1]); } else { puts("IndSet"); int cnt = 0; for (int i = 1; i <= 3 * n&&cnt < n; i++) { if (!vis[i]) { printf("%d%c", i, " \n"[cnt++ == n - 1]); } } } } return0; }