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

using namespace std;

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

int n, m, ctcNr;
bool fr[100100], frTrans[100100];
vector<int> adj[100100], adjTrans[100100], ctc[100100];
stack<int> s;

void dfs(int node)
{
    fr[node] = 1;
    for(auto it: adj[node])
        if(!fr[it])
            dfs(it);
    s.push(node);
}

void dfsTrans(int node)
{
    ctc[ctcNr].push_back(node);
    frTrans[node] = 1;
    for(auto it: adjTrans[node])
        if(!frTrans[it])
            dfsTrans(it);
}

void kosaraju()
{
    for(int i = 1; i <= n; i++)
        if(!fr[i])
            dfs(i);

    while(!s.empty())
    {
        int node = s.top();
        if(!frTrans[node])
        {
            ctcNr++;
            dfsTrans(node);
        }
        s.pop();
    }
}

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

    kosaraju();

    out << ctcNr << '\n';
    for(int i = 1; i <= ctcNr; i++)
    {
        for(auto it: ctc[i])
            out << it << ' ';
        out << '\n';
    }

    return 0;
}