#include <fstream>
#include <vector>
#include <bitset>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");

#define nmax 100010

int n,m,nrc,x,y;
vector<int> g[nmax],gt[nmax],c[nmax],ord;
bitset<nmax> viz;

void dfs(int nod)
{
    vector<int>::iterator it;
    viz.set(nod);
    for (it=g[nod].begin();it!=g[nod].end();it++)
        if (viz.test(*it)==false)
            dfs(*it);
    ord.push_back(nod);
}

void dfst(int nod)
{
    vector<int>::iterator it;
    viz.reset(nod);
    c[nrc].push_back(nod);
    for (it=gt[nod].begin();it!=gt[nod].end();it++)
        if (viz.test(*it)==true)
            dfst(*it);
}

int main()
{
    int i,j;
    vector<int>::iterator it;
    cin>>n>>m;
    for (i=1;i<=m;i++)
    {
        cin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
    for (i=1;i<=n;i++)
        if (viz.test(i)==false)
            dfs(i);
    for (it=ord.end();it!=ord.begin();it--)
        if (viz.test(*(it-1))==true)
        {
            nrc++;
            dfst(*(it-1));
        }
    cout<<nrc<<'\n';
    for (i=1;i<=nrc;i++)
    {
        for (it=c[i].begin();it!=c[i].end();it++)
            cout<<*it<<" ";
        cout<<'\n';
    }
}