#include <bits/stdc++.h>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

const int nmax=1e5+5;
int n,m,comp[nmax];

vector <int> gr1[nmax],gr2[nmax],rez[nmax];
stack <int> st;

bool viz[nmax];

void dfs1(int nod)
{
    viz[nod]=true;
    for (int vec:gr1[nod] )
        if ( !viz[vec] )
            dfs1(vec);

    st.push(nod);
}

void dfs2(int nod, int cnx)
{
    comp[nod]=cnx;
    for (int vec:gr2[nod] )
        if ( comp[vec]==-1 )
            dfs2(vec,cnx);

}

int main()
{
    f >> n >> m;
    for (int i=1; i<=m; i++ )
    {
        int x,y; f >> x >> y;
        gr1[x].push_back(y);
        gr2[y].push_back(x);
    }

    for (int i=1; i<=n; i++ )
        if ( !viz[i] )
            dfs1(i);

    for (int i=1; i<=n; i++ )
        comp[i]=-1;

    int cnx=0;
    while ( !st.empty() )
    {
        int x=st.top(); st.pop();
        if ( comp[x]==-1 )
            dfs2(x,cnx++);
    }

    g << cnx << '\n';
    for (int i=1; i<=n; i++ )
        rez[comp[i]].push_back(i);

    for (int i=0; i<cnx; i++, g << '\n' )
        for (auto j:rez[i] )
            g << j << " ";

    return 0;
}