///50p
#include <bits/stdc++.h>
#define NM 100001
using namespace std;

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

int n, ctc[NM], nrc;
bool Plus[NM], Minus[NM];
vector <int> G[NM], GT[NM];

void df1(int x)
{
	Plus[x] = 1;
	for(int i=0; i < (int)G[x].size(); ++i)
		if(Plus[G[x][i]] == 0)
			df1(G[x][i]);
}

void df2(int x) ///graful transpus
{
	Minus[x] = 1;
	for(int i=0; i < (int)GT[x].size(); ++i)
		if(Minus[GT[x][i]] == 0)
			df2(GT[x][i]);
}

int main()
{
    int i , j , m;
    f >> n >> m;
    while( m-- ) {
    	f >> i >> j;
    	G[i].push_back(j);
    	GT[j].push_back(i); ///graful transpus
    }

    for(int i = 1 ; i <= n ; ++i)
        if(ctc[i] == 0){
            memset(Plus, 0, n+1);
            memset(Minus, 0, n+1);
            nrc ++;
            df1(i);
        	df2(i);
            for(int j = 1; j <= n ; ++j)
                    if(Plus[j] == 1 && Minus[j] == 1)
                        ctc[j] = nrc;
		}

    g << nrc << "\n";
    for(int i=1; i<=nrc; ++i){
        for(int j=1; j<=n; ++j)
            if (ctc[j] == i) g << j << " ";
        g << '\n';
    }

    return 0;
}