#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

int n, m, i, x, y, k;
vector<int> adj[100100], revadj[100100], compon[100100];
bool viz[100100];
stack<int> ord;

void dfs(int node)
{
    viz[node] = true;
    for (vector<int>::iterator it = adj[node].begin(); it != adj[node].end(); advance(it, 1))
    {
        if (!viz[(*it)])
            dfs((*it));
    }
    ord.push(node);
}

void revdfs(int node)
{
    viz[node] = true;
    for (vector<int>::iterator it = revadj[node].begin(); it != revadj[node].end(); advance(it, 1))
    {
        if (!viz[(*it)])
            revdfs((*it));
    }
    compon[k].push_back(node);
}

int main()
{
    f >> n >> m;
    for (i = 1; i <= m; i++) {
        f >> x >> y;
        adj[x].push_back(y);
        revadj[y].push_back(x);
    }
    for (i = 1; i <= n; i++) {
        if (!viz[i]) {
            dfs(i);
        }
    }
    for (i = 1; i <= n; i++)
        viz[i] = false;
    while (!ord.empty()) {
        i = ord.top();
        ord.pop();
        if (!viz[i]) {
            k++;
            revdfs(i);
        }
    }
    g << k << '\n';
    for (i = 1; i <= k; i++) {
        for (vector<int>::iterator it = compon[i].begin(); it != compon[i].end(); advance(it, 1))
        {
            g << (*it) << ' ';
        }
        g << '\n';
    }

    f.close();
    g.close();
    return 0;
}