#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <stack>
#include <algorithm>
#include <map>
#include <set>

using namespace std;
fstream f("ctc.in", ios::in), g("ctc.out", ios::out);
vector<int> adj[50001], adjtranspirat[50001], v[50001], vans[50001];
stack<int> s;
bool abis[50001];
int ans;
void dfs(int x)
{
    if (!abis[x])
    {
        abis[x] = 1;
        for (int i = 0; i < adj[x].size(); i++)
        {
            int vecin = adj[x][i];
            dfs(vecin);
        }
        s.push(x);
    }
}
void dfstranspirat(int x)
{
    if (!abis[x])
    {
        v[ans].push_back(x);
        abis[x] = 1;
        for (int i = 0; i < adjtranspirat[x].size(); i++)
        {
            int vecin = adjtranspirat[x][i];
            dfstranspirat(vecin);
        }
    }
}
int main()
{
    int n, m;
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        f >> x >> y;
        adj[x].push_back(y), adjtranspirat[y].push_back(x);
    }

    for (int i = 1; i <= n; i++)
        dfs(i);

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

    while (!s.empty())
    {
        int nod = s.top();
        s.pop();
        if (!abis[nod])
        {
            dfstranspirat(nod);
            sort(v[ans].begin(), v[ans].end());
            vans[v[ans][0]] = v[ans];
            ans++;
        }
    }
    g << ans << '\n';
    for (int i = 1; i <= n; i++)
    {
        if (vans[i].size())
        {
            for (const auto& x : vans[i])
                g << x << ' ';
            g << '\n';
        }
    }
}