#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <algorithm>
#include <set>
using namespace std;

#define mp make_pair
#define pb push_back
#define x first
#define y second
#define pii pair<int, int>
#define pdd pair<double, double>
#define pid pair<int, double>
#define pdi pair<double, int>
#define ppi pair<pair<int, int>, int>
#define forit(it, v) for(__typeof(v.begin()) it = v.begin(); it != v.end(); ++it)
#define sz(v) v.size()
#define del(it, v) v.erase(it)
#define db double
#define ll long long

const int INF = 0x3f3f3f3f;
const int MAX_N = 100010;
const int MAX_M = 0;
const int MAX_L = 0;

int n, m, sol, z;
int a[MAX_N], f[MAX_N];
vector <int> v[MAX_N], vt[MAX_N], s[MAX_N];

void df(int nod)
{
	if (f[nod])
		return;
	f[nod] = 1;

	forit(it, v[nod])
		df(*it);

	a[++z] = nod;
}

void df2(int nod)
{
	if (f[nod] == 2)
		return;
	f[nod] = 2;

	s[sol].pb(nod);

	forit(it, vt[nod])
		df2(*it);
}

int main()
{
	int i;
	freopen("ctc.in", "r", stdin);
	freopen("ctc.out", "w", stdout);

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

	for (i = 1; i <= m; ++i)
	{
		int r1, r2;

		scanf("%d %d", &r1, &r2);

		v[r1].pb(r2);
		vt[r2].pb(r1);
	}

	for (i = 1; i <= n; ++i)
		if (!f[i])
			df(i);

	for (i = n; i; --i)
		if (f[a[i]] != 2)
		{
			++sol;
			df2(a[i]);
		}

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

	for (i = 1; i <= sol; ++i)
	{
		forit(it, s[i])
			printf("%d ", *it);
		printf("\n");
	}
}