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

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

const int nmax=1e5+3;

int n,m,a,b,viz[nmax],p,k,actual,viz2[nmax],nod;
vector <int> x[nmax],y[nmax],sol[nmax];
stack <int> stiva;

void dfs1(int nod)
{
    viz[nod]=1;
    for(int i=0;i<x[nod].size();++i)
    {
        if(viz[x[nod][i]]) continue;
        dfs1(x[nod][i]);
    }
    stiva.push(nod);
}
void dfs2(int nod)
{
    viz2[nod]=p;
    for(int i=0;i<y[nod].size();++i)
    {
        if(viz2[y[nod][i]]) continue;
        dfs2(y[nod][i]);
    }
    sol[p].push_back(nod);
}
int main()
{
    f>>n>>m;
    while(m--)
    {
        f>>a>>b;
        x[a].push_back(b);
        y[b].push_back(a);
    }
    for(int i=1;i<=n;++i) if(!viz[i]) dfs1(i);
    while(!stiva.empty())
    {
        nod=stiva.top();
        stiva.pop();
        if(viz2[nod]) continue;
        ++p;
        actual=viz[nod];
        dfs2(nod);
    }
    g<<p<<'\n';
    for(int i=1;i<=p;++i)
    {
        for(int j=0;j<sol[i].size();++j) g<<sol[i][j]<<' ';
        g<<'\n';
    }
    return 0;
}

//plec dintr o parte a grafului cu dfs1, salvez ordinea in stiva sol
//ma folosesc de stiva pentru a parcurge invers, folosesc dfs2 si salvez ordinea in vectorul sol
//afisez la final vectorul sol