#include <cstdio>
#include <queue>
#include <vector>
using namespace std;
struct E
{
    int v, t;
} e[100050];
queue<int> q;
vector<int> v[100050], g[100050];
bool b[100050];
int n, m, c, _, C, L, d[100050], l[100050], h[100050], P[100050], S[100050], I[100050];
void A(int u, int v) { e[++c] = {v, h[u]}, h[u] = c; }
void T(int u)
{
    d[u] = l[u] = ++_, b[S[++L] = u] = 1;
    for (int i = h[u], v; i; i = e[i].t)
        if (!d[v = e[i].v])
            T(v), l[u] = min(l[u], l[v]);
        else if (b[v])
            l[u] = min(l[u], d[v]);
    if (d[u] == l[u])
    {
        ++C;
        int z = -1;
        while (z != u)
            b[z = S[L--]] = 0, v[P[z] = C].push_back(z);
    }
}
int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 0, u, v; i < m; ++i)
        scanf("%d%d", &u, &v), A(u, v);
    for (int i = 0; i < n; ++i)
        if (!d[i])
            T(i);
    printf("%d\n", C);
    for (int u = 0; u < n; ++u)
        for (int i = h[u], v; i; i = e[i].t)
            if (P[u] != P[v = e[i].v])
                g[P[u]].push_back(P[v]), ++I[P[v]];
    for (int i = 1; i <= C; ++i)
        if (!I[i])
            q.push(i);
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        printf("%d ", v[u].size());
        for (auto i : v[u])
            printf("%d ", i);
        puts("");
        for (auto v : g[u])
            if (!--I[v])
                q.push(v);
    }
    return 0;
}