#include <bits/stdc++.h>

using namespace std;
const int N = 5e5 + 10, M = 4e6 + 10;

//边双模板
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++;
}

int dfn[N], low[N], stk[N], timestamp, top;
int n, m;

int bcc_cnt;
vector<int> bcc[N]; //边双中有哪些点

void tarjan(int u, int from) {
    dfn[u] = low[u] = ++timestamp;
    stk[++top] = u;

    for (int i = h[u]; ~i; i = ne[i]) {
        int j = e[i];
        if (!dfn[j]) {
            tarjan(j, i); // j:点，i:哪条边
            low[u] = min(low[u], low[j]);
        } else if (i != (from ^ 1))
            low[u] = min(low[u], dfn[j]);
    }

    if (dfn[u] == low[u]) {
        ++bcc_cnt; //边双数量+1
        int x;
        do {
            x = stk[top--];
            bcc[bcc_cnt].push_back(x); // 记录边双中有哪些点
        } while (x != u);
    }
}

int main() {
//文件输入输出
#ifndef ONLINE_JUDGE
    freopen("P8436.in", "r", stdin);
#endif
    scanf("%d %d", &n, &m);
    memset(h, -1, sizeof h);
    for (int i = 1; i <= m; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
        if (a != b) add(a, b), add(b, a);
    }

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

    //输出边双个数
    printf("%d\n", bcc_cnt);
    for (int i = 1; i <= bcc_cnt; i++) {
        printf("%d ", bcc[i].size());
        for (int j : bcc[i]) printf("%d ", j);
        printf("\n");
    }
    return 0;
}