#include<bits/stdc++.h>
#define NMAX 100005
using namespace std;

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

vector<int>G[NMAX],GT[NMAX];
vector<int>Ras[NMAX];

bool used[NMAX];
int care[NMAX];
vector<int>Ordine;
int cate=1;
int n,m;

void DFS(int node)
{
    used[node]=true;
    for(auto i:G[node])
        if(used[i]==false)
    {
        DFS(i);
    }
    Ordine.push_back(node);
}

void DFST(int node,int unde)
{
    care[node]=unde;
    for(auto i:GT[node])
    {
        if(care[i]==0)
            DFST(i,unde);
    }
}

int main()
{
    f>>n>>m;
    for(int i=1;i<=m;++i)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(int i=1;i<=n;++i)
    {
        if(used[i]==false)
        {
            DFS(i);
        }
    }
    for(;Ordine.size();Ordine.pop_back())
    {
        if(care[Ordine.back()]==0)
        {
            DFST(Ordine.back(),cate);
            cate++;
        }
    }
    for(int i=1;i<=n;++i)
        Ras[care[i]].push_back(i);
    g<<cate-1<<'\n';
    for(int i=1;i<cate;++i)
    {
        for(auto j:Ras[i])
            g<<j<<' ';
        g<<'\n';
    }
}