#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define lsb(x) (x & (-x))

using namespace std;

const int MAXN = (int) 1e5;

	vector <int> g[MAXN + 1], gr[MAXN + 1];
bool vis[MAXN + 1];
vector <int> top;

void dfs(int nod) {
	vis[nod] = 1;
	for(auto it : g[nod]) {
		if(vis[it] == 0) {
			dfs(it);
		}
	}
	top.push_back(nod);
}

vector <vector <int>> sol;

void dfs1(int nod) {
	sol.back().push_back(nod);
	vis[nod] = 1;
	for(auto it : gr[nod]) {
		if(vis[it] == 0) {
			dfs1(it);
		}
	}
}

int main() {
#ifdef HOME
	ifstream cin("A.in");
	ofstream cout("A.out");
#endif
	ifstream cin("ctc.in");
	ofstream cout("ctc.out");
	int i, n, m;
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	
	cin >> n >> m;
	for(i = 1; i <= m; i++) {
		int x, y; cin >> x >> y;
		g[x].push_back(y);
		gr[y].push_back(x);
	}
	for(i = 1; i <= n; i++) {
		if(vis[i] == 0) {
			dfs(i);
		}
	}
	memset(vis, 0, sizeof(vis));
	while(top.size()) {
		if(vis[top.back()] == 0) {
			sol.push_back(vector <int>());
			dfs1(top.back());
		}
		top.pop_back();
	}
	
	cout << sol.size() << "\n";
	for(auto &it : sol) {
		for(auto nod : it) {
			cout << nod << " ";
		}
		cout << "\n";
	}
	
	return 0;
}