#include <iostream>
#include <fstream>
#include <forward_list>
#include <stack>
#include <vector>
#include <algorithm>

using namespace std;

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

int n,m,a,b,t,cnt;
bool viz1[100005],viz2[100005];
forward_list < int > v1[200005];
forward_list < int > v2[200005];
vector < int > v[100005];
stack < int > s;

void DFS1(int x)
{
    viz1[x]=1;
    for(auto it=v1[x].begin(); it!=v1[x].end();it++)
        if(!viz1[*it])
            DFS1(*it);
    s.push(x);
}

void DFS2(int x)
{
    viz2[x]=1;
    v[cnt].push_back(x);
    for(auto it=v2[x].begin(); it!=v2[x].end();it++)
        if(!viz2[*it])
            DFS2(*it);
}

int main()
{
    fin >> n >> m;
    for(;m;--m)
    {
        fin >> a >> b;
        v1[a].push_front(b);
        v2[b].push_front(a);
    }
    for(int i=1;i<=n;i++)
        if(!viz1[i])
            DFS1(i);
    while(!s.empty())
    {
        t=s.top();
        s.pop();
        if(!viz2[t])
        {
            cnt++;
            DFS2(t);
            sort(v[cnt].begin(),v[cnt].end());
        }
    }
    fout << cnt << '\n';
    for(int i=1;i<=cnt;i++)
    {
        for(auto it=v[i].begin();it!=v[i].end();it++)
            fout << *it << " ";
        fout << '\n';
    }
    return 0;
}