#include <bits/stdc++.h>
#define DIM 100005

using namespace std;

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

int n, m, nrCTC;
stack <int> s;
bitset <DIM> viz;
vector <int> edges[DIM], edges1[DIM], ctc[DIM];

void dfs(int node)
{
    viz[node] = 1;
    for (auto child: edges[node])
        if (!viz[child])
            dfs(child);
    s.push(node);
}

void dfs1(int node)
{
    viz[node] = 1;
    ctc[nrCTC].push_back(node);
    for (auto child: edges1[node])
        if (!viz[child])
            dfs1(child);
}

int main()
{
    f >> n >> m;

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        f >> x >> y;
        edges[x].push_back(y);
        edges1[y].push_back(x);
    }

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

    viz.reset();

    while(!s.empty())
    {
        if(!viz[s.top()])
        {
            nrCTC++;
            dfs1(s.top());
        }
        s.pop();
    }

    g << nrCTC << "\n";
    for (int i = 1; i <= nrCTC; i++, g << "\n")
        for (auto k: ctc[i])
            g << k << " ";

    return 0;
}