#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <bitset>
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

using VI = vector<int>;
using VVI = vector<VI>;

VVI G, cc;
VI niv, L, c;
int n, m, nv, a, b;
bitset<100001> inStack;
stack<int> stk;

void ReadGraph();
void Tarjan(int nod);

int main()
{
    ReadGraph();

    for ( int i = 1; i <= n; ++i )
        if ( niv[i] == 0 )
            nv = 0, Tarjan(i);

    fout << cc.size() << "\n";

    for (const auto& c : cc)
    {
		for (const auto& x : c)
			fout << x << ' ';
		fout << '\n';
	}

    fin.close();
    fout.close();
    return 0;
}

void Tarjan(int x)
{
    niv[x] = L[x] = ++nv;
    stk.push(x);
    inStack[x] = true;

    for ( const auto& y : G[x] )
        if ( niv[y] == 0 ) // muchie de arbore
        {
            Tarjan(y);
            L[x] = min(L[x], L[y]);
        }
        else  // sa fie muchie de intoarcere, nu muchie transversala
            if ( inStack[y] )
                L[x] = min(L[x], niv[y]);

    // daca nod e radacina, scoatem din stiva comp tare conexa curenta (stiva nu se goleste neaparat)
    if ( niv[x] == L[x] )
    {
        c.clear();
        int x2;
        while ( true )
        {
            c.push_back(x2 = stk.top());
            stk.pop();
            inStack[x2] = false;
            if ( x2 == x )
				break;
        }
        cc.push_back(c);
    }

}

void ReadGraph()
{
    fin >> n >> m;
    G = VVI(n + 1);
    L = niv = VI(n + 1);

    for (int i = 1; i <= m; ++i )
    {
        fin >> a >> b;
        G[a].push_back(b);
    }
}