#include <iostream>
#include <stdio.h>
#include <vector>
#include <stack>

#define Nmax 100005

using namespace std;

vector<int> CC[Nmax];
vector<int> Gi[Nmax];
vector<int> G[Nmax];
stack<int> S;

int vizi[Nmax];
int viz[Nmax];
int n, m;
int nrc;

void citire()
{
    int x, y;
    scanf("%d %d\n", &n, &m);
    for(int i=1; i<=m; ++i)
    {
        scanf("%d %d\n", &x, &y);
        G[x].push_back(y);
        Gi[y].push_back(x);
    }
}

void parcurgere(int vf)
{
    viz[vf] = 1;

    for(vector<int>::iterator it = G[vf].begin(); it != G[vf].end(); ++it)
    {
        if(!viz[*it])
            parcurgere(*it);
    }
    S.push(vf);
}


void dfs(int k)
{
    vizi[k] = 1;

    for(vector<int>::iterator it = Gi[k].begin(); it != Gi[k].end(); ++it)
    {
        if(!vizi[*it])
        {
            CC[nrc].push_back(*it);

            dfs(*it);
        }
    }
}


void afisare()
{
    /*
    while(!S.empty())
    {
        printf("%d ", S.top());
        S.pop();
    }
    */
    printf("%d\n", nrc);
    for(int i=0; i<nrc; ++i)
    {
        for(vector<int>::iterator it = CC[i].begin(); it!=CC[i].end(); ++it)
            printf("%d ", *it);
        printf("\n");
    }
}

void sol1()
{
    for(int i = 1; i<=n; ++i)
        if(!viz[i])
            parcurgere(i);
}

void sol2()
{
    while(!S.empty())
    {
        int aux = S.top();
        S.pop();
        if(!vizi[aux])
        {
            CC[nrc].push_back(aux);
            dfs(aux);
            nrc++;
        }
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);

    citire();
    sol1();
    sol2();
    afisare();
    return 0;
}