#include <bits/stdc++.h>

#define FOR(i, l, r) for (int i = l; i < (r); ++i)
#define F0R(i, r) FOR (i, 0, r)
#define ROF(i, l, r) for (int i = r; i-- > (l);)
#define R0F(i, r) ROF (i, 0, r)
#define rep(n) F0R (_, n)
#define each(i, x) for (auto& i : x)

using namespace std;

using ll = long long;
using db = long double;
using str = string;

using pi = pair<int, int>;
#define mp make_pair
#define f first
#define s second

#define ttt template <typename T
ttt > using vec = vector<T>;
ttt, size_t n > using arr = array<T, n>;
using vi = vec<int>;
using vb = vec<bool>;
using vl = vec<ll>;
using vpi = vec<pi>;

#define sz(x) int((x).size())
#define bg begin
#define all(x) bg(x), end(x)
#define sor(x) sort(all(x))
#define rsz resize
#define pb push_back
#define eb emplace_back

#define il inline
#define lb lower_bound
#define ub upper_bound
ttt > il int lwb(const vec<T>& a, const T& v) { return lb(all(a), v) - bg(a); }
ttt > il int upb(const vec<T>& a, const T& v) { return ub(all(a), v) - bg(a); }

ttt > il bool ckmin(T& x, const T& y) { return y < x ? x = y, true : false; }
ttt > il bool ckmax(T& x, const T& y) { return x < y ? x = y, true : false; }

int main() {
  cin.tie(nullptr)->sync_with_stdio(false), cin.exceptions(cin.failbit);

  int n, m;
  cin >> n >> m;

  vec<vpi> adj(n);
  vpi e(m);
  F0R (i, m) {
    auto& [u, v] = e[i];
    cin >> u >> v;
    adj[u].eb(v, i), adj[v].eb(u, i);
  }

  int ti = 0, top = -1;
  vi dfn(n), low(n), stk(n);
  vec<vi> bccs;
  auto dfs = [&](auto dfs, int u, int p, int e) -> void {
    dfn[u] = low[u] = ++ti, stk[++top] = u;
    for (auto [v, i] : adj[u]) {
      if (i == e) continue;
      if (dfn[v])
        ckmin(low[u], dfn[v]);
      else
        dfs(dfs, v, u, i), ckmin(low[u], low[v]);
    }
    if (p == -1 || low[u] > dfn[p]) {
      vi bcc;
      for (int x = -1; x != u;) bcc.pb(x = stk[top--]);
      bccs.eb(move(bcc));
    }
  };
  F0R (i, n)
    if (!dfn[i]) dfs(dfs, i, -1, -1);
  cout << sz(bccs) << "\n";
  each (bcc, bccs) {
    cout << sz(bcc);
    each (i, bcc) cout << " " << i;
    cout << "\n";
  }
}