#include <fstream>
#include <stack>
#include <vector>
#define MAXN  100005
#define Min(a, b)  ((a) < (b) ? (a) : (b))
using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
vector <int> adj[MAXN], con, idx, lowlink, in_stack;
vector < vector <int> > C;
stack <int> S;
int indecs;
void tarjan(const int n, const vector <int>* adj)
{
    idx[n] = lowlink[n] = indecs;
    indecs ++;
    S.push(n), in_stack[n] = 1;
    vector <int>::const_iterator it;
    for (it = adj[n].begin(); it != adj[n].end(); ++ it) {
        if (idx[*it] == -1) 
			tarjan(*it, adj),   lowlink[n] = Min(lowlink[n], lowlink[*it]);
        else if (in_stack[*it]) lowlink[n] = Min(lowlink[n], lowlink[*it]);
    }
    if (idx[n] == lowlink[n])
	{
        con.clear();
		int node;
        do
		{
            con.push_back(node = S.top());
            S.pop(), in_stack[node] = 0;
        }
        while (node != n);
        C.push_back(con);
    }
}
int main()
{
    int n;
    int cnt_edges, x, y;
    in >> n;
    for (in >> cnt_edges; cnt_edges > 0; -- cnt_edges)
        in >> x >> y, adj[x - 1].push_back(y - 1);
    in.close();
    idx.resize(n), lowlink.resize(n), in_stack.resize(n);
    idx.assign(n, -1), in_stack.assign(n, 0);
    for (int i = 0; i < n; ++ i) 
		if (idx[i] == -1) tarjan(i, adj);
     out << C.size() << "\n";
    for (size_t i = 0; i < C.size(); ++ i) 
	{		
        for (size_t j = 0; j < C[i].size(); ++ j) out << C[i][j] + 1 << " ";
        out << "\n";
    }
    return 0;
}