#include <iostream>
#include <stdio.h>
#include <vector>
using namespace std;

vector<int> l[100050];
vector<int> lt[100050];
int s[100050],st[100050],vis[100050],c = 0;
vector<vector<int>> res;
vector<int> v;
inline void add(int i, int j){
	l[i].push_back(j);
	lt[j].push_back(i);
}

void dfsi(int i){
	vector<int> n = l[i];
	s[i] = 1;
	for(int j = 0; j < n.size(); j++){
		if(s[n[j]] == 0){
			s[n[j]] = 1;
			dfsi(n[j]);
		}
	}
	vis[c++] = i;

}
void dfst(int i){
	vector<int> n = lt[i];
	st[i] = 1;
	for(int j = 0; j < n.size(); j++){
		if(st[n[j]] == 0){
			st[n[j]] = 1;
			dfst(n[j]);
		}
	}
	v.push_back(i);
}

int main(){
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	int n,m;
	scanf("%d%d",&n,&m);
	for(int i = 0; i < m; i++){
		int x,y;
		scanf("%d%d",&x,&y);
		add(x,y);
	}

	for(int i = 1; i < n; i++)
		if(s[i] == 0)
			dfsi(i);

	for(int i = c - 1; i >= 0; i--){
		if(!st[vis[i]]){
			dfst(vis[i]);
			res.push_back(v);
			v.clear();
		}

	}
	printf("%u\n",res.size());
	for(int i = 0; i < (int)res.size(); i++){
		for(int j = 0; j < res[i].size(); j++)
			printf("%d ",res[i][j]);
		printf("\n");
	}
	return 0;
}