#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
bool v[50001];
vector< vector<int> > g, gt;
stack<int> st;
int n, m, q, cnt, a[5001][5001];
void dfs(int na)
{
v[na] = 1;
for (int i = 0; i < g[na].size(); ++ i)
if (v[g[na][i]] == 0)
dfs(g[na][i]);
st.push(na);
}
void dfst(int na)
{
v[na] = 0;
for (int i = 0; i < gt[na].size(); ++ i)
if (v[gt[na][i]] == 1)
dfst(gt[na][i]);
a[cnt][++ q] = na;
}
void read()
{
fin >> n >> m;
g.resize(n + 1);
gt.resize(n + 1);
int x, y;
for (int i = 1; i <= m; ++ i)
{
fin >> x >> y;
g[x].push_back(y);
gt[y].push_back(x);
}
}
int main()
{
read();
for (int i = 1; i <= n; ++ i)
if (v[i] == 0) dfs(i);
while(!st.empty())
{
if(v[st.top()])
{
q = 0;
cnt ++;
dfst(st.top());
a[cnt][0] = q;
}
st.pop();
}
fout << cnt;
for (int i = 1; i <= cnt; ++ i)
{
fout <<'\n';
for (int j = 1; j <= a[i][0]; ++ j)
fout << a[i][j] <<' ';
}
return 0;
}