#include <cstdio>
#include <vector>
#include <stack>
using namespace std;

#define nmax 100000
long n, m, k;
bool viz[nmax+1];
vector <long> v[nmax];
vector <long> vt[nmax];
vector <long> cc[nmax];
stack <long> S;

void citire()
{
	long x, y;
	freopen("ctc.out", "w", stdout); freopen("ctc.in", "r", stdin);
	scanf("%ld %ld", &n, &m);
	for(long i=1; i<=m; i++)
	{
		scanf("%ld %ld", &x, &y);
		v[x].push_back(y);
		vt[y].push_back(x);
	}
}

void afisare()
{
	printf("%ld \n", k);
	for(long i=1; i<=k; i++)
	{
		for(long j=0; j<cc[i].size(); j++)
			printf("%ld ", cc[i][j]);
		printf("\n");
	}

}

void dfst(int nod)
{
	viz[nod] = false; cc[k].push_back(nod); 
	for(long i=0; i<vt[nod].size(); i++)
		if( viz[ vt[nod][i] ] == true)
			dfst( vt[nod][i] );
	
}

void dfs(int nod)
{
	viz[nod] = true;
	for(long i=0; i<v[nod].size(); i++)
		if( viz[ v[nod][i] ] == false )
			dfs( v[nod][i] );
	S.push(nod);
}

void kosaraju()
{
	for(long i=1; i<=n; i++)
		if( viz[i] == false )
			dfs(i);
		
	while( !S.empty() )
	{
		if( viz[ S.top() ] == true)
		{	
			k++;
			dfst(S.top());
		}
		S.pop();
	}
}

int main()
{
	citire();
	kosaraju();
	afisare();
	return 0;
}