#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#include <bitset>
#define N 100005

using namespace std;

int n, nr;

vector <int> G[N], invers[N], de_afisat[N];

stack <int> S;

bitset <N> viz;

void recursiv1(int x)
{
    vector <int>::iterator it;

    viz[x] = true;

    for(it = G[x].begin(); it != G[x].end(); ++it)
    {
        if(!viz[*it])
        {
            recursiv1(*it);
        }
    }

    S.push(x);
}

void recursiv2(int x)
{
    de_afisat[nr].push_back(x);

    vector <int>::iterator it;

    viz[x] = true;

    for(it = invers[x].begin(); it != invers[x].end(); ++it)
    {
        if(!viz[*it])
        {
            recursiv2(*it);
        }
    }
}

void afisare()
{
    printf("%d\n",nr);

    vector <int>::iterator it;

    for(int i = 0 ; i < nr; ++i)
    {
        for(it = de_afisat[i].begin(); it != de_afisat[i].end(); ++it)
        {
            printf("%d ",*it);
        }
        printf("\n");
    }
}

void prelucrare()
{
    for(int i = 1 ; i <= n; ++i)
    {
        if(!viz[i])
        {
            recursiv1(i);
        }
    }

    viz.reset();

    while(!S.empty())
    {
        int tmp = S.top();

        S.pop();

        if(!viz[tmp])
        {
            recursiv2(tmp);

            ++nr;
        }
    }

    afisare();
}

void citire()
{
    int m;

    scanf("%d %d\n",&n,&m);

    for(int i = 0; i < m; ++i)
    {
        int a,b;

        scanf("%d %d\n",&a,&b);

        G[a].push_back(b);

        invers[b].push_back(a);
    }
    prelucrare();
}

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

    citire();

    return 0;
}