#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
bool visited[100001];
vector<int> graph1[100001];
vector<int> graph2[100001];
vector<int> ctc[100001];
int q, k, s[100001];
void dfs1(int node) {
visited[node] = true;
for(auto n : graph1[node])
if(!visited[n])
dfs1(n);
s[++k] = node;
}
void dfs2(int node) {
visited[node] = false;
ctc[q].push_back(node);
for(auto n : graph2[node])
if(visited[n] == 1)
dfs2(n);
}
int main() {
int n, m;
fin >> n >> m;
for(int i = 1; i <= m; i++) {
int x, y;
fin >> x >> y;
graph1[x].push_back(y);
graph2[y].push_back(x);
}
for(int i = 1; i <= n; i++) {
if(!visited[i]) {
dfs1(i);
}
}
for(int i = n; i >= 1; i--) {
if(visited[s[i]] == 1) {
q++;
dfs2(s[i]);
}
}
fout << q << endl;
for(int i = 1; i <= q; i++) {
for(auto node : ctc[i])
fout << node << ' ';
fout << endl;
}
}