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

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

const int N=100005;

vector< int > a[N],c[N];
vector< int > b[N];
int n,m,tps[N],ncc,k;
bool viz[N];

void citire()
{
    int i,x,y;
    in>>n>>m;
    for(i=1; i<=m; i++)
    {
        in>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }
    in.close();
}
void dfs1(int nod)
{
    int i,vecin;
    viz[nod]=1;
    for(i=0; i<(int)a[nod].size(); i++)
    {
        vecin=a[nod][i];
        if(!viz[vecin])
            dfs1(vecin);
    }
    tps[++k]=nod;
}

void dfs2(int nod)
{
    int i,vecin;
    viz[nod]=1;
    c[ncc].push_back(nod);
    for(i=0; i<(int)b[nod].size(); i++)
    {
        vecin=b[nod][i];
        if(!viz[vecin])
            dfs2(vecin);
    }
}
int main()
{
    int i,j;
    citire();
    for(i=1; i<=n; i++)
        if(!viz[i])
            dfs1(i);
    for(i=1; i<=n; i++)
        viz[i]=0;
    for(i=n; i>=1; i--)
    {
        if(viz[tps[i]]==0)
        {
            ncc++;
            dfs2(tps[i]);
        }
    }
    out<<ncc<<'\n';
    for(i=1; i<=ncc; i++)
    {
        for(j=0; j<(int)c[i].size(); j++)
            out<<c[i][j]<<" ";
        out<<endl;
    }
    return 0;
}