#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
#include <cstring>

using namespace std;

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

const int DIM = 50005;

int n,m,x,y,viz[DIM],cnt=0;

stack <int> St;

vector <int> G[DIM];
vector <int> P[DIM];
vector <int> Sol[DIM];

void DFS1(int nod)
{
    viz[nod]=1;
    for(auto it : G[nod])
    {
        if(!viz[it])
            DFS1(it);
    }
    St.push(nod);
}

void Read()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        P[y].push_back(x);
    }
}

void DFS2(int nod)
{
    viz[nod]=1;
    Sol[cnt].push_back(nod);
    for(auto it : P[nod])
    {
        if(!viz[it])
            DFS2(it);
    }
}

void Solve()
{
    for(int i=1;i<=n;i++)
    {
        if(!viz[i])
            DFS1(i);
    }
    memset(viz,0,sizeof(viz));
    while(!St.empty())
    {
        int k=St.top();
        if(!viz[k])
        {
            cnt++;
            DFS2(k);
        }
        St.pop();
    }
}

void Print()
{
    fout<<cnt<<'\n';
    for(int i=1;i<=cnt;i++)
    {
        for(auto it : Sol[i])
            fout<<it<<" ";
        fout<<'\n';
    }
}

int main()
{
    Read();
    Solve();
    Print();
}