#include <bits/stdc++.h>

using namespace std;

int n, m, x, y;
bool viz[100005];
bool viz2[100005];
int v[100005];

struct node{
    node *next;
    int inf;
};
node *L[100005];
node *K[100005];

void add(node *&start, int inf) {
    node *one = new node;
    one->inf = inf;
    one->next = start;
    start = one;
}

void dfs(int in) {
    viz[in] = true;
    for(node *p = L[in]; p; p = p->next) {
        if(!viz[p->inf])
            dfs(p->inf);
    }
}

void dfs2(int in) {
    viz2[in] = true;
    for(node *p = K[in]; p; p = p->next) {
        if(!viz2[p->inf])
            dfs2(p->inf);
    }
}

int main()
{
    FILE *f = fopen("ctc.in", "r");
    FILE *g = fopen("ctc.out", "w");
    fscanf(f, "%d %d", &n, &m);
    for(int i = 1; i <= m; i ++) {
        fscanf(f, "%d %d", &x, &y);
        add(L[x], y);
        add(K[y], x);
    }

    int nr = 0;
    for(int i = 1; i <= n; i ++) {
        if(!v[i]) {
            nr ++;
            dfs(i);
            dfs2(i);
            for(int j = 1; j <= n; j ++) {
                if(viz[j] && viz2[j]) {
                    v[j] = nr;
                }
                viz[j] = false;
                viz2[j] = false;
            }
        }
    }
    fprintf(g, "%d\n", nr);
    while(nr) {
        for(int i = 1; i <= n; i ++) {
            if(v[i] == nr)
                fprintf(g, "%d ", i);
        }
        fprintf(g, "\n");
        nr --;
    }
    return 0;
}