#include <bits/stdc++.h>
#define N 100007
using namespace std;

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

int n,m,ct,temp;
vector<int>a[N],comp[N];
vector<int> low_link(N,0),disc(N,0);
vector<bool>instack(N,0);
stack<int>st;

void Citire()
{
    fin >> n >> m;
    for(int i=1;i<=m;i++)
    {
        int x,y;fin >> x >> y;
        a[x].push_back(y);
    }
    fin.close();
}

void DFS(int x)
{
    disc[x]=++temp;
    low_link[x]=disc[x];
    st.push(x);
    instack[x]=1;
    for(auto y:a[x])
    {
        if( disc[y] )
        {
            if( instack[y] )
                low_link[x]=min(low_link[x],disc[y]);
        }
        else
        {
            DFS(y);
            low_link[x]=min(low_link[x],low_link[y]);
        }
    }
    if( low_link[x]==disc[x] )
    {
        ct++;
        while( st.top()!=x )
        {
            comp[ct].push_back(st.top());
            instack[st.top()]=0;
            st.pop();
        }
        comp[ct].push_back(st.top());
        st.pop();
    }
}

void Tarjan()
{
    for(int i=1;i<=n;i++)
        if( !disc[i] )
            DFS(i);
}

void Sortare_Afisare()
{
    for(int i=1;i<=ct;i++)
        sort( comp[i].begin(),comp[i].end() );
    bool ok=1;
    while(ok)
    {
        ok=!ok;
        for(int i=1;i<=ct-1;i++)
            if( comp[i][0]>comp[i+1][0] )
            {
                ok=1;
                swap(comp[i],comp[i+1]);
            }
    }
    fout << ct << "\n";
    for(int i=1;i<=ct;i++,fout<<'\n')
        for(auto y:comp[i])
            fout << y << " ";

}

int main()
{
    Citire();
    Tarjan();
    Sortare_Afisare();
    return 0;
}