#include <bits/stdc++.h>
using namespace std;

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

vector<int> L[100005] , T[100005] , C[100005];
int viz[100005] , n , m , a[100005] , p , nrcc;

void DFST(int k)
{
    viz[k] = 1;
    for(int i : L[k])
        if(viz[i] == 0) DFST(i);
    a[++p] = k;
}

void DFS(int k)
{
    viz[k] = 1;
    C[nrcc].push_back(k);
    for(int i : T[k])
        if(viz[i] == 0) DFS(i);
}

int main()
{
    int i , j , k;
    fin >> n >> m;
    for(k = 1;k <= m;k++)
    {
        fin >> i >> j;
        L[i].push_back(j);
        T[j].push_back(i);
    }
    for(k = 1;k <= n;k++)
        if(viz[k] == 0) DFST(k);
    for(k = 1;k <= n;k++)
        viz[k] = 0;
    for(k = n;k >= 1;k--)
        if(viz[a[k]] == 0)
        {
            nrcc++;
            DFS(a[k]);
        }
    fout << nrcc << "\n";
    for(k = 1;k <= nrcc;k++)
    {
        for(int i : C[k])
            fout << i << " ";
        fout << "\n";
    }
    return 0;
}