#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream f ("ctc.in");
ofstream g ("ctc.out");
int n, m;
vector<int> v[100005];
vector<int> vr[100005];
vector<int> sk;
int viz[100005], viz2[100005];
vector<vector<int>> componente;
//i'll use kosaraju's algorithm
//step 1: we do a dfs and we order the verteces by finish time in decreasing order in a stack
//step 2: we reverse the graph and we start with the first element in the stack
// we start a dfs from this element and the elemnts that we visit will be the first
// strongly conected graph

void dfs(int x)
{
    if(viz[x]==0)
    {
        viz[x]=1;
        for(int i=0; i<v[x].size(); i++)
        {
            if(viz[v[x][i]]==0)
                dfs(v[x][i]);
        }
        sk.push_back(x);
    }
}
void dfs_reverse(int x, int index)
{
    if(viz2[x]==0)
    {
        viz2[x]=1;
        componente[index].push_back(x);
        for(int i=0; i<vr[x].size(); i++)
        {
            if(viz2[vr[x][i]]==0)
                dfs_reverse(vr[x][i], index);
        }
    }
}

int main()
{
    f>>n>>m;
    for(int i=0; i<m; i++)
    {
        int x, y;
        f>>x>>y;
        v[x].push_back(y);
        vr[y].push_back(x);
    }

    int modificari=1;
    while(modificari==1)
    {
        modificari=0;
        for(int i=1; i<=n; i++)
        {
            if(viz[i]==0)
            {
                dfs(i);
                modificari=1;
            }
        }
    }

    int index=0;
    reverse(sk.begin(), sk.end());
    modificari=1;
    while(modificari==1)
    {
        modificari=0;
        for(int i=0; i<n; i++)
        {
            if(viz2[sk[i]]==0)
            {
                vector<int> r;
                componente.push_back(r);
                dfs_reverse(sk[i], index);
                modificari=1;
                index++;
            }
        }
    }
    g<<componente.size()<<"\n";
    for(int i=0; i<componente.size(); i++)
    {
            for(int j=0; j<componente[i].size(); j++)
            {
                g<<componente[i][j]<<" ";
            }
            g<<"\n";
    }
    return 0;
}