#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define debug(...) fprintf(stderr, ##__VA_ARGS__)
#else
#define endl "\n"
#define debug(...) void(0)
#endif
using LL = long long;
constexpr int N = 2e5 + 10;
int n, m;
vector<pair<int, int>> g[N];
vector<vector<int>> eccs;
int dfn[N], low[N], stk[N], ecc, cnt, top, col[N];
void tarjan(int u, int fid) {
  dfn[u] = low[u] = ++cnt, stk[++top] = u;
  for (auto e : g[u]) {
    int v = e.first, id = e.second;
    if (!dfn[v]) tarjan(v, id), low[u] = min(low[u], low[v]);
    else if (id != fid) low[u] = min(low[u], dfn[v]);
  }
  if (low[u] == dfn[u]) {
    ++ecc;
    vector<int> one;
    do col[stk[top]] = ecc, one.push_back(stk[top]); while (stk[top--] != u); 
    eccs.push_back(one);
  }
}
int main() {
#ifndef LOCAL
  cin.tie(nullptr)->sync_with_stdio(false);
#endif
  cin >> n >> m;
  for (int i = 1, u, v; i <= m; i++) cin >> u >> v, ++u, ++v, g[u].emplace_back(v, i), g[v].emplace_back(u, i);
  for (int i = 1; i <= n; i++) if (!dfn[i]) tarjan(i, 0);
  cout << eccs.size() << endl;
  for (auto vec : eccs) {
    cout << vec.size();
    for (int x : vec) cout << " " << x - 1;
    cout << endl;
  }
  return 0;
}