#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

using namespace std;

typedef long long ll;
#define all(x) begin(x), end(x)
constexpr int INF = (1 << 30) - 1;
constexpr long long IINF = (1LL << 60) - 1;
constexpr int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

template <class T> istream& operator>>(istream& is, vector<T>& v) {
    for (auto& x : v) is >> x;
    return is;
}

template <class T> ostream& operator<<(ostream& os, const vector<T>& v) {
    auto sep = "";
    for (const auto& x : v) os << exchange(sep, " ") << x;
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) { return y < x and (x = forward<U>(y), true); }

template <class T, class U = T> bool chmax(T& x, U&& y) { return x < y and (x = forward<U>(y), true); }

template <class T> void mkuni(vector<T>& v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <class T> int lwb(const vector<T>& v, const T& x) { return lower_bound(begin(v), end(v), x) - begin(v); }

const int MAX = 10;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<vector<int>> G(n);
    for (int i = 0; i < n - 1; i++) {
        int x, y;
        cin >> x >> y;
        x--, y--;
        G[x].emplace_back(y);
        G[y].emplace_back(x);
    }

    vector<int> sub(n), alive(n, true);
    auto dfs_sz = [&](auto self, int v, int p) -> int {
        sub[v] = 1;
        for (int& u : G[v]) {
            if (u == p or not alive[u]) continue;
            sub[v] += self(self, u, v);
        }
        return sub[v];
    };
    auto dfs_search_centroid = [&](auto self, int v, int p, int mid) -> int {
        for (int& u : G[v]) {
            if (u == p or not alive[u]) continue;
            if (sub[u] > mid) return self(self, u, v, mid);
        }
        return v;
    };
    vector<vector<int>> ans(MAX);
    auto solve = [&](auto self, int r, int d) -> void {
        assert(d < 10);
        int c = dfs_search_centroid(dfs_search_centroid, r, -1, dfs_sz(dfs_sz, r, -1) / 2);
        ans[d].emplace_back(c);
        alive[c] = false;
        for (int& ch : G[c]) {
            if (not alive[ch]) continue;
            self(self, ch, d + 1);
        }
    };
    solve(solve, 0, 0);
    while (ans.back().empty()) ans.pop_back();
    reverse(begin(ans), end(ans));

    cout << ans.size() << '\n';
    for (auto& v : ans) {
        cout << v.size();
        for (int& x : v) cout << ' ' << x + 1;
        cout << '\n';
    }
    return 0;
}