#include <stdlib.h>
#include <stdio.h>
 
struct node
{
    int data;
    struct node *next;
};
 
int list_add_front(struct node **head, int val)
{
    struct node *tmp;
    tmp = malloc(sizeof(struct node));
    tmp->data = val;
    tmp->next = *head;
 
    *head = tmp;
    return 0;
}
 
 
int list_pop_front(struct node **head, int *val)
{
    struct node *tmp;
    *val = (*head)->data;
 
    tmp = *head;
    *head = (*head)->next;
 
    free(tmp);
    return 0;
}
 
int dfs(struct node **graph, int root, int *marked, int conr, int *order, int* oidx)
{
    if (marked[root])
        return 0;
 
    marked[root] = conr;
    for(struct node* p = graph[root]; p != NULL; p = p->next)
        if(!marked[p->data])
            dfs(graph, p->data, marked, conr, order, oidx);
 
    if (order != NULL)
        order[(*oidx)++] = root;
 
    return 0;
}
 
int main()
{
    FILE *infile, *outfile;
    int n, m, i;
    int *order, *marked;
    struct node **grapht, **graph, **comp;  
    int count = 0, oidx = 0;
     
    infile = fopen("ctc.in", "r");
    outfile = fopen("ctc.out", "w");
     
    fscanf(infile, "%d %d", &n, &m);
    marked = malloc((n+1) * sizeof(int));
    order = malloc((n+1) * sizeof(int));
    graph = malloc((n+1) * sizeof(struct node*));
    grapht = malloc((n+1) * sizeof(struct node*));
 
    for (i = 0; i <= n; i++) {
        marked[i] = 0;
        graph[i] = NULL;
        grapht[i] = NULL;
    }
     
    for (i = 0; i < m; i++) {
        int u, v;
        fscanf(infile, "%d %d", &u, &v);
        // add reverse
        list_add_front(&grapht[v], u);
        list_add_front(&graph[u], v);
    }
     
    for (i = 1; i <=n; i++) 
        dfs(grapht, i, marked, 1, order, &oidx);
     
     
    for (i = 1; i <=n; i++)
        marked[i] = 0;
 
    for(i = oidx - 1; i >= 0; i--) {
        if(marked[order[i]])
            continue;
        count++;
        dfs(graph, order[i], marked, count, NULL, NULL);
    }
     
    fprintf(outfile, "%d\n", count);
    comp = malloc((count + 1) * sizeof(struct node*));
    for (i = 0; i <= count; i++)
	comp[i] = NULL;

    for (i = 1; i <= n; i++)
	list_add_front(&comp[marked[i]],i);

    for (i = 1; i <=count; i++) {
        for(struct node* p = comp[i]; p!=NULL; p = p->next)
	    fprintf(outfile, "%d ", p->data);
        fprintf(outfile, "\n");
    }
 
    fclose(infile);
    fclose(outfile);
    return 0;
}