#include <bits/stdc++.h>

using namespace std;

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

int n, m, x, y, cnt, vf, stk[100100];
vector <int> v[100100], vv[100100];
bool viz[100100];
vector <int> sol[100100];

void predfs(int from){
	viz[from] = 1;
	for(auto to : v[from])
		if(!viz[to])
			predfs(to);
	stk[++vf] = from;
}

void dfs(int from){
	viz[from] = 0;
	sol[cnt].push_back(from);
	for(auto to : vv[from])
		if(viz[to])
			dfs(to);
}

int main(){
	in >> n >> m;	
	while(m--){
		in >> x >> y;
		v[x].push_back(y);
		vv[y].push_back(x);
	}
	for(int i = 1; i <= n; i++)
		if(!viz[i])
			predfs(i);
	for(; vf; vf--)
		if(viz[stk[vf]]){
			cnt++;
			dfs(stk[vf]);
		}	
	out << cnt << '\n';
	for(int i = 1; i <= cnt; i++, out << '\n')
		for(auto nod : sol[i])
			out << nod << ' ';
	return 0;
}