#include <bits/stdc++.h>
using namespace std;
const int N = 1010, M = 1010;
int n, m;
int dfn[N], low[N], stk[N], ts, top, root;

int bcnt;
vector<int> bcc[N];
bool cut[N];

int e[M], h[N], idx, w[M], ne[M];
void add(int a, int b, int c = 0) {
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
}

void tarjan(int u, int fa) {
    low[u] = dfn[u] = ++ts;
    stk[++top] = u;
    int son = 0;
    for (int i = h[u]; ~i; i = ne[i]) {
        int v = e[i];
        if (v == fa) continue;
        if (!dfn[v]) {
            son++;
            tarjan(v, u);
            low[u] = min(low[u], low[v]);

            if (low[v] >= dfn[u]) {
                int x;
                if (u != root || son > 1) cut[u] = 1;
                bcnt++;
                do {
                    x = stk[top--];
                    bcc[bcnt].push_back(x);
                } while (x != v);
                bcc[bcnt].push_back(u);
            }
        } else
            low[u] = min(low[u], dfn[v]);
    }

    if (fa == -1 && son == 0) bcc[++bcnt].push_back(u);
}

int main() {
#ifndef ONLINE_JUDGE
    freopen("396_Prepare.in", "r", stdin);
#endif
    memset(h, -1, sizeof h);
    scanf("%d", &m);
    while (m--) {
        int a, b;
        scanf("%d %d", &a, &b);
        n = max(n, a), n = max(n, b); // 鄙视一下~
        if (a != b) add(a, b), add(b, a);
    }

    for (root = 1; root <= n; root++)
        if (!dfn[root]) tarjan(root, -1);

    cout << "点双个数：" << bcnt << endl;

    for (int i = 1; i <= bcnt; i++) {
        cout << "点双编号:" << i << ", 内部节点：";
        for (int j = 0; j < bcc[i].size(); j++)
            cout << bcc[i][j] << " ";
        cout << endl;
    }
    return 0;
}