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

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

const int NMAX=100005;

stack < int > S;

vector < int >  Ad[NMAX] , Add[NMAX];

vector < int > sol[NMAX];

int ct;

int viz[NMAX],viz2[NMAX]; int N,M;

void read()
{
    fin>>N>>M;  int x,y;

    for(int i=1;i<=M;++i)
    {
        fin>>x>>y;

        Ad[x].push_back(y);
        Add[y].push_back(x);
    }
}

void DFS(int u)
{
    int w;

    viz[u]=1;

    for(int i=0;i<Ad[u].size();++i)
    {
        w=Ad[u][i];

        if(viz[w]==0)
            DFS(w);
    }

    S.push(u);
}

void Dfs(int u)
{
    sol[ct].push_back(u);
    viz2[u]=1;

    int w;

    for(int i=0;i<Add[u].size();++i)
    {
        w=Add[u][i];

        if(viz2[w]==0)
        {
            Dfs(w);
        }
    }
}

void Do()
{
    for(int i=1;i<=N;++i)
        if(viz[i]==0) DFS(i);

    int nod;

    while(!S.empty())
    {
        nod=S.top();
        S.pop();

        if(viz2[nod]==0)
            {
             ct++;
             Dfs(nod);
            }
    }

    fout<<ct<<"\n";

    for(int i=1;i<=ct;++i)
    {
        for(int j=0;j<sol[i].size();++j)
            fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
}

int main()
{
    read();
    Do();
    return 0;
}