#include <fstream>
#include <vector>
using namespace std;
const int NMAX = 100001;

int n, m, nrc;

vector<int> G[NMAX], GT[NMAX], CTC[NMAX], Post;

bool viz[NMAX];

ifstream f("ctc.in");
ofstream g("ctc.out");

void citire() {
    int x, y;
    f >> n >> m;
    while(m--) {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfs(int vf) {
    viz[vf] = 1;
    for(int x : G[vf])
        if(viz[x] == 0)
            dfs(x);
    Post.push_back(vf);
}

void dfsGT(int vf) {
    viz[vf] = 0;
    CTC[nrc].push_back(vf);
    for(int x : GT[vf])
        if(viz[x] == 1)
            dfsGT(x);
}

void componente() {
    int i;
    for(i = 1; i <= n; i++)
        if(viz[i] == 0)
            dfs(i);
    for(i = Post.size() - 1; i >= 0; i--)
        if(viz[Post[i]] == 1) {
            nrc++;
            dfsGT(Post[i]);
        }
}

void afisare() {
    g << nrc << '\n';
    for(int i = 1; i <= nrc; i++) {
        for(int x : CTC[i])
            g << x << ' ';
        g << '\n';
    }
}

int main() {
    citire();
    componente();
    afisare();
    f.close();
    g.close();
    return 0;
}