#include <bits/stdc++.h>

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