#include <bits/stdc++.h>

using namespace std;

int n, m, x, y;
int viz[100005];
int viz2[100005];
int V[100005];
struct node{
    node *next;
    int inf;
};
node *L[100005];

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

int nr;

void dfs(int in) {
    viz[in] = 1;
    for(node *p = L[in]; p; p = p->next) {
        if(!viz[p->inf])
            dfs(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);
    }
    for(int i = 1; i < n; i ++) {
        for(int j = i + 1; j <= n; j++) {
                for(int k = 1; k <= n; k ++)
                    viz[k] = 0;
                dfs(i);
                if(viz[i] && viz[j]) {
                    for(int k = 1; k <= n; k ++) {
                        viz[k] = 0;
                    }
                    dfs(j);
                    if(viz[i] && viz[j]) {
                        if(V[i])
                            V[j] = V[i];
                        else if(V[j])
                            V[i] = V[j];
                        else nr ++, V[i] = nr, V[j] = nr;
                    }
                }
        }
    }
    fprintf(g, "%d\n", nr);
    for(int k = 1; k <= nr; k ++) {
        for(int i = 1; i <= n; i ++) {
            if(V[i] == k) {
                fprintf(g, "%d ", i);
            }
        }
        fprintf(g, "\n");
    }
    return 0;
}