#include <stdio.h>
#include <vector>
#include <stack>
#define NMAX 100005

FILE* fin, * fout;

int n, m;
std::vector<int> G[NMAX], GT[NMAX];
int nr = 0;
std::vector<int> res[NMAX];
std::stack<int> s;
bool viz[NMAX];

void dfs(int u) {
	if (viz[u] == true)
		return;
	viz[u] = true;
	for (int v : G[u])
		dfs(v);
	s.push(u);
}

void dfs_t(int u) {
	if (viz[u] == true)
		return;
	viz[u] = true;
	res[nr].push_back(u);
	for (int v : GT[u])
		dfs_t(v);
}


int main() {
	fin = fopen("ctc.in", "r");
	fout = fopen("ctc.out", "w");

	fscanf(fin, "%i %i", &n, &m);

	while (m--) {
		int x, y;
		fscanf(fin, "%i %i", &x, &y);
		G[x].push_back(y);
		GT[y].push_back(x);
	}

	memset(viz, false, sizeof(viz));
	for (int i = 1;i <= n;++i)
		dfs(i);
	memset(viz, false, sizeof(viz));
	while (!s.empty()) {
		if (!viz[s.top()]) {
			dfs_t(s.top());
			++nr;
		}
		s.pop();
	}

	fprintf(fout,"%i\n", nr);
	for (int i = 0;i < nr;++i) {
		for (int x : res[i])
			fprintf(fout,"%i ", x);
		fprintf(fout,"\n");
	}

	return 0;
}