#include <bits/stdc++.h>

using namespace std;

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

int n, m, number, x, y, timp;
bool viz[100001], in_stack[100001];
int componenta[100001], low[100001], disc[100001];
vector<int>G[100001];
vector<int>GT[100001];
vector<int>Gasit;
vector<int>sol[100001];
stack<int>ST;

void DFS(int nod)
{
    viz[nod]=1;
    for(auto it:G[nod]) if(!viz[it]) DFS(it);
    Gasit.push_back(nod);
}

void DFS_T(int nod)
{
    componenta[nod]=number;
    for(auto it:GT[nod]) if(!componenta[it]) DFS_T(it);
}

void Korasaju()
{
    for(int i=1; i<=n; ++i) if(!viz[i]) DFS(i);
    while(Gasit.size()>0)
    {
        if(!componenta[Gasit.back()])
        {
            ++number;
            DFS_T(Gasit.back());
        }
        Gasit.pop_back();
    }
    for(int i=1; i<=n; ++i) sol[componenta[i]].push_back(i);
    fout<<number<<"\n";
    for(int i=1; i<=number; ++i)
    {
        for(auto it:sol[i]) fout<<it<<" ";
        fout<<"\n";
    }
}

void DFS_Tarjan(int nod)
{
    in_stack[nod]=1;
    ST.push(nod);
    //fout<<nod<<" ";
    disc[nod]=low[nod]=++timp;
    for(auto it:G[nod])
    {
        if(!disc[it])
        {
            DFS_Tarjan(it);
            low[nod]=min(low[nod], low[it]);
        }
        else if(in_stack[it]) low[nod]=min(low[nod], disc[it]);
    }

    if(low[nod]==disc[nod])
    {
        ++number;
        while(ST.top()!=nod)
        {
            in_stack[ST.top()]=0;
            sol[number].push_back(ST.top());
            ST.pop();
        }
        in_stack[ST.top()]=0;
        sol[number].push_back(ST.top());
        ST.pop();
    }
}

void Tarjan()
{
    timp=0;
    number=0;
    for(int i=1; i<=n; ++i) if(!disc[i]) DFS_Tarjan(i);
    fout<<number<<"\n";
    for(int i=1; i<=number; ++i)
    {
        for(auto it:sol[i]) fout<<it<<" ";
        fout<<"\n";
    }
}

int main()
{
    fin>>n>>m;
    for(int i=1; i<=m; ++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    //Korasaju();
    Tarjan();
    return 0;
}