#include <bits/stdc++.h>

using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
const int nx=100002;
vector < int > v[nx];
vector < int > w[nx];
vector < int > c[nx];
deque < int > srt;
bitset < nx > viz;
int n,m,i,j,nc;
void dfs1 (int nod)
{
    viz.set(nod);
    for(vector < int > :: iterator it=v[nod].begin(); it!=v[nod].end(); it++)
        if(viz.test(*it)==false)
            dfs1(*it);
    srt.push_front(nod);
}
void dfs2 (int nod)
{
    viz.set(nod);
    c[nc].push_back(nod);
    for(vector < int > :: iterator it=w[nod].begin(); it!=w[nod].end(); it++)
        if(viz.test(*it)==false)
            dfs2(*it);
}
int main()
{
    in>>n>>m;
    for(; m; m--)
    {
        in>>i>>j;
        v[i].push_back(j);
        w[j].push_back(i);
    }
    for(int i=1; i<=n; i++)
        if(viz.test(i)==false)
            dfs1(i);
    viz.reset();
    for(deque < int > :: iterator it=srt.begin(); it!=srt.end(); it++)
        if(viz.test(*it)==false)
        {
            nc++;
            dfs2(*it);
        }
    out<<nc<<'\n';
    for(int i=1; i<=nc; i++)
    {
        for(vector < int > :: iterator it=c[i].begin(); it!=c[i].end(); it++)
            out<<*it<<' ';
        out<<'\n';
    }
    return 0;
}