#include <iostream>
#include <fstream>
#include <vector>
#define NM 100001
using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

vector <int> G[NM], GT[NM], CTC[NM];
int st[NM], viz[NM];
int n, m, t, k;

void dfs (int x) {
    int i, w;

    viz[x] = 1;

    for (i = 0; i < G[x].size(); ++i) {
        w = G[x][i];
        if (!viz[w]) dfs(w);
    }

    st[++t] = x;
}

void dfst (int x) {
    int i, w;

    viz[x] = 1;
    CTC[k].push_back(x);

    for (i = 0;i < GT[x].size(); ++i) {
        w = GT[x][i];
        if (!viz[w]) dfst(w);
    }
}

int main() {
    int i, j;
    int x, y;

    fin >> n >> m;

    for (i = 1; i <= m; ++i) {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

    for (i = 1; i <= n; ++i)
        if (!viz[i]) dfs(i);

    for (i = 1; i <= n; ++i) viz[i] = 0;

    for (i = n; i >= 1; --i)
        if (!viz[st[i]]) {
            ++k;
            dfst(st[i]);
        }

    fout << k << '\n';
    for (i = 1; i <= k; ++i) {
        for (j = 0; j < CTC[i].size(); ++j)
            fout << CTC[i][j] << ' ';
        fout << '\n';
    }
}