#include<bits/stdc++.h>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> L[100001];
vector <int> T[100001];
vector <int> ctc[100001];
int nrc, n, m, viz[100001];
int st[100001], sol[100001], top;

void DFS1(int k)
{
	viz[k]=1;
	for(auto i : L[k])
		if(viz[i]==0) DFS1(i);
	st[++top]=k;
}

void DFS2(int k)
{
	viz[k]=1;
	for(auto i : T[k])
		if(viz[i]==0) DFS2(i);
	ctc[nrc].push_back(k);
}

void CTC()
{
    int i,j;
	for (i=1;i<=n;i++)
		if (viz[i] == 0) DFS1(i);
	for (i=1;i<=n;i++)
		viz[i] = 0;
	while (top > 0)
	{
		i = st[top];
		top--;
		if (viz[i] == 0)
        {
            nrc++;
            DFS2(i);
        }
    }
    for (i = 1; i <= nrc; i++)
        sort(ctc[i].begin(), ctc[i].end());
    for(i=1;i<=n;i++)
        for(j=0;j<ctc[i].size();j++)
            sol[ctc[i][j]]=i;
}
int main()
{
    int i,x,y,j;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        L[x].push_back(y);
        T[y].push_back(x);
    }
    CTC();
    fout<<nrc<<"\n";
    for(j=1;j<=nrc;j++)
    {
        for(auto z : ctc[j])
            fout<<z<<" ";
        fout<<"\n";
    }
    return 0;
}