/*
    plus-minus
    v 2.0
*/
#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#include <algorithm>
#include <ctime>
#include <utility>

using namespace std;

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

const int N = 100005;

vector <int> G[N] , nodes, Gt[N], adj(N), sol[N], discovered, where(N, -1);
bitset < N > used;

int n, m, ccount;

void read()
{
    cin >> n >> m;
    for(int i = 1 ; i <= m ; ++ i)
    {
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
}
void dfp(int node)         // marchez cu plus
{
    used[node] = 1;
    for(vector<int> :: iterator it = G[node].begin(); it != G[node].end(); ++ it)
        if(!used[*it])
            dfp(*it);
    discovered.push_back(node);
}
void dfm(int node, int which)
{
    where[node] = which;
    for(vector<int> :: iterator it = Gt[node].begin(); it != Gt[node].end(); ++ it)
        if(where[node] == -1)
            dfm(*it, which);
}
void write()
{
    cout << ccount << "\n";
    for(int i = 1 ; i <= ccount; ++ i)
        {for(vector <int> :: iterator it = sol[i].begin(); it != sol[i].end(); ++ it)
            cout << *it << " " ;
        cout << "\n";}

}
int main()
{
    for(int i = 1 ; i <= n ; ++ i)
        if(!used[i])
            dfp(i);
    for(; discovered.size(); discovered.pop_back())
        if(where[discovered.back()] == -1)
        {
            ++ccount;
            dfm(discovered.back() , ccount);
        }
    for(int i = 1 ; i <= ccount; ++ i)
        sol[where[i]].push_back(i);
    write();
    return 0;
}