#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <cstring>
#define nmax 100005

using namespace std;

int n, m, nrComp;
vector <int> G[nmax], GT[nmax], sol[nmax];
bool viz[nmax];
stack <int> s;

void dfs(int nod)
{
    viz[nod] = true;
    for (int i = 0; i < G[nod].size(); i++)
        if (!viz[G[nod][i]])
            dfs(G[nod][i]);
    s.push(nod);
}

void dfsF(int nod)
{
    viz[nod] = true;
    sol[nrComp].push_back(nod);
    for (int i = 0 ; i < GT[nod].size(); i++)
        if (!viz[GT[nod][i]])
            dfsF(GT[nod][i]);
}

int main()
{
    
    ifstream fi("ctc.in");
    ofstream fo("ctc.out");
    
    fi >> n >> m;
    
    for (int i = 1; i <= m; i++)
    {
        int x, y;
        fi >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            dfs(i);
    
    memset(viz, false, sizeof(viz));
    
    for (; s.size();)
    {
        if (!viz[s.top()])
        {
            nrComp++;
            dfsF(s.top());
        }
        s.pop();
    }
    
    fo << nrComp << "\n";
    
    for (int i = 1; i <= nrComp; i++)
    {
        for (int j = 0; j < sol[i].size(); j++)
            fo << sol[i][j] << " ";
        fo << "\n";
    }
    
    
    fi.close();
    fo.close();
    
    return 0;
}