#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

int n, m, nr, viz[100001];
vector<int> G[100001], GT[100001], f;

void dfs(int x) {
    viz[x] = 1;
    for (int i : G[x])
        if (!viz[i])
            dfs(i);
    f.push_back(x);
}

void dfs_t(int x, int val) {
    viz[x] = val;
    for (int i : GT[x])
        if (!viz[i])
            dfs_t(i, val);
}

int main()
{
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs(i);
    for (int i = 1; i <= n; i++)
        viz[i] = 0;
    for (auto it = f.rbegin(); it != f.rend(); it++)
        if (!viz[*it]) {
            nr++;
            dfs_t(*it, nr);
        }
    fout << nr << "\n";
    for (int i = 1; i <= nr; i++) {
        for (int j = 1; j <= n; j++)
            if (viz[j] == i)
                fout << j << " ";
        fout << "\n";
    }
    return 0;
}