#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10, M = 4e6 + 10;

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++;
}

// 点双模板
int dfn[N], low[N], stk[N], ts, top, root;
vector<int> bcc[N];
int bcnt;

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;
                bcnt++;
                do {
                    x = stk[top--];
                    bcc[bcnt].push_back(x);
                } while (x != v);       // 将子树出栈
                bcc[bcnt].push_back(u); // 把割点/树根也丢到点双里
            }
        } else
            low[u] = min(low[u], dfn[v]);
    }
    // 特判独立点
    if (fa == -1 && son == 0) bcc[++bcnt].push_back(u);
}

int n, m;
int main() {
    memset(h, -1, sizeof h);
    scanf("%d %d", &n, &m);
    while (m--) {
        int a, b;
        scanf("%d %d", &a, &b);
        if (a != b) add(a, b), add(b, a);
    }

    for (root = 1; root <= n; root++)
        if (!dfn[root]) tarjan(root, -1);
    // 个数
    printf("%d\n", bcnt);
    for (int i = 1; i <= bcnt; i++) {
        printf("%d ", bcc[i].size());
        for (int j = 0; j < bcc[i].size(); j++)
            printf("%d ", bcc[i][j]);
        printf("\n");
    }
    return 0;
}