#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;

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

const int nmax=100005;
int n,m,x,y,ct;
bool viz1[nmax],viz2[nmax];

stack < int > S;
vector < int > Ad[nmax], Add[nmax] , sol[nmax];

void read()
{
    fin>>n>>m;

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

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

void dfs1(int u)
{
    int w;

    viz1[u]=1;

    for(int i=0;i<Ad[u].size();++i)
    {
        w=Ad[u][i];
        if(viz1[w]==0) dfs1(w);
    }

    S.push(u);
}

void dfs2(int u)
{
    int w;

    viz2[u]=1;
    sol[ct].push_back(u);

    for(int i=0;i<Add[u].size();++i)
    {
        w=Add[u][i];
        if(viz2[w]==0) dfs2(w);
    }
}

void solve()
{
    int nod;

    for(int i=1;i<=n;++i)
        if(viz1[i]==0) dfs1(i);

    while(S.size() > 0)
    {
        nod=S.top();
        S.pop();

        if(viz2[nod]==0)
        {
         ct++;
         dfs2(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();
    solve();
    return 0;
}