#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

void dfs(int v, vector<bool>&visited, vector<vector<int>>&adj, stack<int>&order)
{
    visited[v] = true;
    for(auto a : adj[v])
    {
        if(!visited[a])
            dfs(a, visited, adj, order);
    }
    order.push(v);
}
void dfs2(int v, vector<bool>&visited, vector<vector<int>>&adj, vector<int>&vis)
{
    visited[v] = true;
    for(auto a : adj[v])
    {
        if(!visited[a])
            dfs2(a, visited, adj, vis);
    }
    vis.push_back(v);
}

int main()
{
    int n, m;
    fin >> n >> m;
    vector<vector<int>>adj(n + 1);
    vector<vector<int>>adjtr(n + 1);
    for(int i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        adj[x].push_back(y);
        adjtr[y].push_back(x);
    }

    vector<bool>visited(n+1, false);
    stack<int>order;

    for(int i = 1; i <= n; i++)
    {
        if(!visited[i])
            dfs(i, visited, adj, order);
    }
    vector<vector<int>>comp;
    vector<bool>vis2(n+1, false);
    int cp = 0;
    while(!order.empty())
    {
        int t = order.top();
        order.pop();
        if(!vis2[t])
        {
            cp++;
            vector<int>vis;
            dfs2(t, vis2, adjtr, vis);
            comp.push_back(vis);
        }
    }

    fout << cp << "\n";
    for(auto v : comp)
    {
        for(auto c : v)
            fout << c << " ";
        fout << "\n";
    }
    return 0;
}