#include <fstream>
#include <iostream>
#include <string>
#include <complex>
#include <cmath>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <stack>
#include <algorithm>
#include <list>
#include <bitset>
#include <ctime>
#include <climits>
#include <cassert>
#include <iomanip>

using namespace std;


const string file = "ctc";
const string inputF = file + ".in";
const string outputF = file + ".out";

const double epsilon = 1e-7;
#define LL long long
#define ULL unsigned long long 
#define MOD1 666013
#define MOD2 666019
#define MOD3 1999999973
#define base 73

typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<string> vs;
typedef pair<int, int> ii;
typedef pair<long long, long long> ll;
typedef vector<ii> vii;
typedef vector<ll> vll;

#define all(V) V.begin(), V.end()
#define allr(V) V.rbegin(), V.rend()
#define for_c_it(container, it) for (auto it : container)
#define present(container, element) (container.find(element) != container.end()) 
#define sz(a) int((a).size()) 
#define pb push_back 
#define mp make_pair
#define zeroes(x) ((x ^ (x - 1)) & x)
#define maxn 200001

int N, M, depth, nrcomp;
vvi graph;
vvi comp;
vi index, lowlink, viz;
stack<int> st;

void tarjan(int from) {
	index[from] = lowlink[from] = depth; ++depth;
	st.push(from);
	viz[from] = 0;

	for (auto x: graph[from]) {
		if (viz[x] == -1) {
			tarjan(x);
			lowlink[from] = min(lowlink[from], lowlink[x]);
		}
		else if (viz[x] == 0) {
			lowlink[from] = min(lowlink[from], index[x]);
		}
	}

	if (index[from] == lowlink[from]) {
		comp.pb(vector<int>());
		int node;
		do {
			comp[nrcomp].pb(node = st.top());
			st.pop();
			viz[node] = 1;
		} while(!st.empty() && node != from); 
		++nrcomp;
	}
}


int main() {
#ifndef INFOARENA
	freopen("input.txt", "r", stdin);
#else 
	freopen(inputF.c_str(), "r", stdin);
	freopen(outputF.c_str(), "w", stdout);
#endif
	int i, x, y;
	scanf("%d %d", &N, &M);
	graph.resize(N);
	viz.resize(N, -1);
	index.resize(N);
	lowlink.resize(N);
	
	for (i = 0; i < M; ++i) {
		scanf("%d %d", &x, &y);
		--x; --y;
		graph[x].pb(y);
	}
	
	for (i = 0; i < N; ++i) {
		if (viz[i] == -1) {
			tarjan(i);
		}
	}
	
	printf("%d\n", nrcomp);
	for (auto x: comp) {
		for (auto y: x) {
			printf("%d ", y + 1);
		}
		printf("\n");
	}
	return 0;
}