#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <list>
#include <stack>
#include <ctime>
#include <cassert>
using namespace std;

#define PRO "ctc"
void OpenFiles(int EVAL)
{
	if(EVAL)
	{
		char input[100] = PRO, output[100] = PRO;
		freopen(strcat(input, ".in"),"r",stdin);
		freopen(strcat(output,".out"),"w",stdout);
	} else
	{
		freopen("test.in","r",stdin);
		freopen("test.out","w",stdout);
	}
}

#define MAX 100001
#define MOD 666013
#define INF 0xffffff
#define EPS 1E-8

int n, m, nr;
vector<int>graf[MAX], tran[MAX], comp[MAX];
bool viz[MAX];
stack<int>st;

void dfs(int x)
{
	viz[x] = 1;
	for(int i=0;i<graf[x].size();i++) 
		if(!viz[ graf[x][i] ]) dfs( graf[x][i] );
	st.push(x);
}

void dfs_el(int x)
{
	viz[x] = 1;
	for(int i=0;i<tran[x].size();i++)
		if(!viz[ tran[x][i] ]) dfs_el( tran[x][i] );
	comp[nr].push_back(x);
}

int main(int argv,char *args[])
{	
OpenFiles(argv==0);
	/* start code */
		scanf("%d %d",&n,&m);
		for(int i=1,x,y; i<=m;i++)
		{
			scanf("%d %d",&x,&y);
			graf[x].push_back(y);
			tran[y].push_back(x);
		}
		for(int i=1;i<=n;i++)
			if(!viz[i])
				dfs(i);
		memset(viz,0,sizeof(viz));
		while( !st.empty() )
		{
			nr++;
			dfs_el (st.top());
			while(!st.empty() && viz[st.top()])st.pop();
		}
		printf("%d\n",nr);
		for(int i=1;i<=nr;i++)
		{	for(int j=0;j<comp[i].size();j++) printf("%d ",comp[i][j]); printf("\n"); }
	/* end */
	return 0;
}