#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100000

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

vector<int> v[NMAX],viz,vt[NMAX];
stack <int> s;

void dfs(int k,bool ok=true)
{
    viz[k]=1;
    for(auto x:v[k])
        if(!viz[x])
    {
        viz[x]=1;
        dfs(x,ok);
    }
    if(ok)
        s.push(k);
}

int main()
{
    int n,m;
    f>>n>>m;
    for(int i=0;i<n;++i)
        viz.push_back(0);
    while(m--)
    {
        int x,y;
        f>>x>>y;
        v[x-1].push_back(y-1);
    }

    for(int i=0;i<n;++i)
        if(!viz[i])
            dfs(i);

    for(int i=0;i<n;++i)
    {
        for(auto y:v[i])
            vt[y].push_back(i);
    }
    vector <int> t;
    for(int i=0;i<n;++i)
        {v[i]=vt[i];
        vt[i]=t;}

    for(int i=0;i<n;++i)
        viz[i]=0;

    int nr=0;

    while(!s.empty())
    {
        if(!viz[s.top()])
        {
            ++nr;
            dfs(s.top(),false);
            vt[nr-1].push_back(s.top());
        }
        else
            vt[nr-1].push_back(s.top());

        s.pop();
    }
    g<<nr<<'\n';
    for(int i=0;i<nr;++i)
    {
        for(auto y:vt[i])
            g<<y+1<<' ';
        g<<'\n';
    }

    return 0;
}