#include <stdio.h>
#include <stdlib.h>

#define WHITE 0
#define GRAY 1
#define BLACK 2

typedef struct nod {
    int nr_copil;
    int *kid;
    int culoare;
} Nod;

int N, M, *S, nr_elem, **comp, nr_comp, *aux, n_glob;

FILE *in, *out;

void dfs(Nod *graf, int i)
{
    int j;
    graf[i].culoare = GRAY;
    for (j = 0; j < graf[i].nr_copil; j++)
        if (graf[graf[i].kid[j]].culoare == WHITE)
            dfs(graf, graf[i].kid[j]);
     S[nr_elem++] = i;
     graf[i].culoare = BLACK;
}

void dfsT (Nod *transpus, int i)
{
    int j;
    transpus[i].culoare = GRAY;
    aux[n_glob++] = i;
    for (j = 0; j < transpus[i].nr_copil; j++)
        if (transpus[transpus[i].kid[j]].culoare == WHITE) 
            dfsT(transpus, transpus[i].kid[j]);
            
       
    transpus[i].culoare = BLACK;
}

void ctc (Nod *graf, Nod *transpus)
{
    int i, j, cod = 1, c;
    
    while (cod) {
        for (i = 1; i <= N; i++) {
            c = 0;
            for (j = 0; j < nr_elem; j++)
                if (S[j] == i) {
                    c = 1;
                    break;
                 }
             if (c == 0) {//nodul nu e pe stiva
                dfs(graf, i);
                break;
             }
         if (c == 1)
            cod = 0;
         }
    }
    
    while (nr_elem > 0) { 
        i = S[nr_elem - 1];
        nr_elem --;  
        n_glob = 0;
        dfsT(transpus, i);
        if (n_glob > 1) {
            nr_comp++;
            comp = realloc(comp, (nr_comp + 1) * sizeof(int*));
            comp[nr_comp] = calloc(N, sizeof(int));
            comp[nr_comp - 1][0] = n_glob;
            for (j = 0; j < n_glob; j++) {
                comp[nr_comp - 1][j + 1] = aux[j];
             }   
        }
    }
    
}

void afisare (FILE *out, Nod *graf)
{
    int i,j;
    for (i = 1; i <= N; i++) {
        printf("%d: ", i);
        for (j = 0; j < graf[i].nr_copil; j++)
            printf("%d ", graf[i].kid[j]);
        printf("\n");
    }
}

void print()
{
    int i,j ;
    fprintf(out, "%d\n", nr_comp);
    for(i = 0; i < nr_comp; i++) {
        for (j = 0; j < comp[i][0]; j++)
            fprintf(out,"%d ", comp[i][j+1]);
        fprintf(out,"\n"); 
    }
}
int main()
{
    int i, x, y;
    
    in = fopen("ctc.in","r");
    out = fopen("ctc.out","w");
    
    fscanf(in, "%d", &N); //nr de noduri
    fscanf(in, "%d", &M); //nr de muchii
    
    Nod *graf, *transpus;
    graf = calloc(N + 1, sizeof(Nod));
    transpus = calloc(N + 1, sizeof(Nod));
    S = calloc(N + 1, sizeof(int));
    nr_comp = 0;
    comp = calloc(1, sizeof(int *));
    comp[0] = calloc(N + 1, sizeof(Nod));
    aux = calloc(N + 1, sizeof(Nod));
    nr_elem = 0;
    for (i = 0; i <= N; i++) {
        graf[i].nr_copil = 0;
        graf[i].culoare = WHITE;
        transpus[i].nr_copil = 0;
        transpus[i].culoare = WHITE;
    }
    
    for (i = 0; i < M; i++) {
        fscanf(in, "%d", &x);
        fscanf(in, "%d", &y);
        graf[x].nr_copil ++;
        graf[x].kid = realloc(graf[x].kid, graf[x].nr_copil * sizeof(int));
        graf[x].kid[graf[x].nr_copil - 1] = y;
        transpus[y].nr_copil ++;
        transpus[y].kid = realloc(transpus[y].kid, transpus[y].nr_copil * sizeof(int));
        transpus[y].kid[transpus[y].nr_copil - 1] = x;        
    }
    
//    afisare(out, transpus);    
    ctc(graf, transpus);
    print();
    fclose(in);
    fclose(out);
    return 0;
}