#include <bits/stdc++.h>

using namespace std;

const int MAXN = 1e5 + 10;

vector< int > gr[MAXN];
vector< int > gri[MAXN];
vector< int > order;
vector< int > sol[MAXN];
int cnt = 0;

bool viz[MAXN];

void dfs(int node) {
	viz[node] = 1;
	for(auto &x : gr[node]) {
		if(!viz[x]) dfs(x);
	}

	order.emplace_back(node);
}
void dfs1(int node) {
	viz[node] = 0;
	sol[cnt].emplace_back(node);
	for(auto &x : gri[node]) {
		if(viz[x]) dfs1(x);
	}
}
int main() {
	#ifdef BLAT
		freopen("input", "r", stdin);
	#else
		freopen("ctc.in", "r", stdin);
		freopen("ctc.out", "w", stdout);
	#endif

	int n, m;
	scanf("%d%d", &n, &m);

	for(int i = 0; i < m; ++i) {
		int a, b;
		scanf("%d%d", &a, &b);
		gr[a].emplace_back(b);
		gri[b].emplace_back(a);
	}

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

	reverse(order.begin(), order.end());

	for(int i = 0; i < n; ++i) {
		if(viz[order[i]]) {
			++cnt;
			dfs1(order[i]);
		}
	}

	printf("%d\n", cnt);

	for(int i = 1; i <= cnt; ++i) {
		for(auto &x : sol[i]) {
			printf("%d ", x);
		}
		printf("\n");
	}
}