#include <fstream>
#include <vector>
#include <bitset>

using namespace std;

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

const int N = 100001;

vector <int> a_s[N] , a_p[N] ;
vector <vector<int>> ctc ;
bitset <N> viz ;
int n , m , sol[N] , nrs , cc[N];

void dfs(int x)
{
    viz[x] = 1;
    for ( auto y: a_s[x] )
    {
        if ( !viz[y] )
        {
            dfs(y);
        }
    }
    sol[++nrs] = x;
}

void dfs_p( int x )
{
    viz[x] = 1;
    cc[x] = ctc.size() - 1;
    for ( auto y: a_p[x] )
    {
        if ( !viz[y] )
        {
            dfs_p(y);
        }
    }
}

int main()
{
    in >> n >> m;
    for ( int i = 0 ; i < m ; i++ )
    {
        int x, y;
        in >> x >> y;
        a_s[x].push_back(y);
        a_p[y].push_back(x);
    }
    in.close();
    for ( int i = 1 ; i <= n ; i++ )
    {
        if ( !viz[i] )
        {
            dfs(i);
        }
    }
    viz.reset();
    for ( int i = nrs ; i >= 1 ; i-- )
    {
        if ( !viz[sol[i]] )
        {
            vector <int> v;
            ctc.push_back(v);
            dfs_p(sol[i]);
        }
    }
    out << ctc.size() << "\n";
    for ( int i = 1 ; i <= n ; i++ )
    {
        ctc[cc[i]].push_back(i);
    }
    for ( auto comp: ctc )
    {
        for ( auto x: comp )
        {
            out << x << " ";
        }
        out << "\n" ;
    }
    out.close();
    return 0;
}