#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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

const int dim = 100002;
bool viz[dim];
vector<int> a[dim], t[dim], finished, rez[dim];


void dfs(int x)
{
    viz[x] = 1;
    for (auto y : a[x])
        if (!viz[y])
            dfs(y);
    finished.push_back(x);
}

void dfs_t(int x, int c)
{   
    
    rez[c].push_back(x);
    viz[x] = 1;
    for (auto y : t[x])
        if (!viz[y])
            dfs_t(y, c);
}

int main()
{
    int n, m, x, y, nrc = 0;
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        a[x].push_back(y);
        t[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs(i);
    reverse(finished.begin(), finished.end());
    for (int i = 1; i <= n; i++)
        viz[i] = 0;
    for (auto x : finished)
        if (!viz[x])
        {
            nrc++;
            dfs_t(x,nrc);
        }
    fout << nrc << '\n';
    for(int i {1}; i <= nrc; ++i) {
        for(int x : rez[i]) {
            fout << x << " ";
        }
        fout << '\n';
    }
    
    return 0;
}