#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

#define local_persist static

typedef vector<int>::iterator iter;
typedef vector<int>::reverse_iterator riter;

#define MAXN 100002

ifstream f("ctc.in");
ofstream g("ctc.out");
#if !INFOARENA
#define g cout
#endif

int n;
vector<int> G[MAXN];
vector<int> Gt[MAXN];
vector< vector<int> > components;

vector<int> order;
void doOrder(int nd);

vector<int> component;
bitset<MAXN> viz;
void findComponent(int nd) {
    if (viz[nd]) {
        return;
    }
    viz[nd] = 1;

    for (iter it = Gt[nd].begin(); it != Gt[nd].end(); it++) {
        findComponent(*it);
    }
    component.push_back(nd);
}

int main()
{
    int m;
    f >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        f >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }

    for (int i = 1; i <= n; i++) {
        doOrder(i);
    }

    for (riter it = order.rbegin(); it != order.rend(); it++) {
        if (!viz[*it]) {
            component.clear();
            findComponent(*it);
            components.push_back(component);
        }
    }

    g << components.size() << '\n';
    for (size_t i = 0; i < components.size(); i++) {
        for (iter it = components[i].begin(); it != components[i].end(); it++) {
            g << *it << ' ';
        }
        g << '\n';
    }

    return 0;
}


void doOrder(int nd) {
    local_persist bitset<MAXN> viz;
    if (viz[nd] == 1) {
        return;
    }
    viz[nd] = 1;

    for (iter it = G[nd].begin(); it != G[nd].end(); it++) {
        doOrder(*it);
    }
    order.push_back(nd);
}