#include <cstdio>
#include <cstring>
#include <list>
#include <stack>
using namespace std;
#define pb push_back
const int MAXN = 100010;

int n, nr;
list<int> vecini[MAXN];
list<int> vecinit[MAXN];
int sel[MAXN];
stack<int> st;
stack<int> st2;
list<int> ctc[MAXN];

void read();
void solve();
void write();
void dfs(int);
void dfst(int);

int main()
{
	read();
	solve();
	write();
	return 0;
}

void dfs(int nod)
{
	st.push(nod);
	list<int>::iterator it = vecini[nod].begin(), sfarsit = vecini[nod].end();
	for (; it != sfarsit; ++it)
	{
		if (!sel[*it])
		{
			sel[*it] = 1;
			dfs(*it);
		}
	}
}

void dfs2(int nod)
{
	ctc[nr].pb(nod);
	list<int>::iterator it = vecinit[nod].begin(), sfarsit = vecinit[nod].end();
	for (; it != sfarsit; ++it)
	{
		if (!sel[*it])
		{
			sel[*it] = 1;
			dfs2(*it);
		}
	}
}

void solve()
{
	nr = 0;
	int i;
	for (i = 1; i <= n; ++i)
	{
		if (!sel[i])
		{
			sel[i] = 1;
			dfs(i);
			for (; !st.empty(); st.pop())
			{
				st2.push(st.top());
			}
		}
	}
	memset(sel, 0, sizeof(sel));
	for (; !st2.empty(); st2.pop())
	{
		i = st2.top();
		if (!sel[i])
		{
			++nr;
			sel[i] = 1;
			dfs2(i);
		}
	}
}

void read()
{
	int i, m, x, y;
	FILE *fin = fopen("ctc.in", "r");
	fscanf(fin, "%d%d", &n, &m);
	for (i = 1; i <= m; ++i)
	{
		fscanf(fin, "%d%d", &x, &y);
		vecini[x].pb(y);
		vecinit[y].pb(x);
	}
	fclose(fin);
}

void write()
{
	int i;
	list<int>::iterator it, sfarsit;
	FILE *fout = fopen("ctc.out", "w");
	fprintf(fout, "%d\n", nr);
	for (i = 1; i <= nr; ++i)
	{
		sfarsit = ctc[i].end();
		for (it = ctc[i].begin(); it != sfarsit; ++it)
		{
			fprintf(fout, "%d ", *it);
		}
		fprintf(fout, "\n");
	}
	fclose(fout);
}