#include <fstream>
#include <stack>
#include <vector>

using namespace std;

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

int n, m, idx, nrc;
vector<vector<int>> G, CC;
vector<int> Index, L, C;
vector<bool> InStack;
stack<int> Stk;

void Read();
void Tarjan(int nod);
void Write();

int main()
{
    Read();
    for (int i = 1; i <= n; i++)
        if (Index[i] == 0) Tarjan(i);
    fout << nrc << '\n';
    Write();
    fin.close();
    fout.close();
    return 0;
}

void Tarjan(int nod)
{
    Index[nod] = L[nod] = ++idx;
    Stk.push(nod);
    InStack[nod] = true;
    for (const auto & x : G[nod])
        if (Index[x] == 0)
        {
            Tarjan(x);
            L[nod] = min(L[nod], L[x]);
        }
        else if (InStack[x])
            L[nod] = min(L[nod], Index[x]);
    if (Index[nod] == L[nod])
    {
        nrc++;
        C.clear();
        int nod2;
        do
        {
            C.push_back(nod2 = Stk.top());
            Stk.pop();
            InStack[nod2] = false;
        } while ( nod2 != nod );
        CC.push_back(C);
    }

}

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

}

void Read()
{
    fin >> n >> m;
    G = vector<vector<int>>(n + 1);
    Index = L = vector<int>(n + 1);
    InStack = vector<bool>(n + 1);
    for (int i = 1, x, y; i <= m; i++)
    {
        fin >> x >> y;
        G[x].push_back(y);
    }
}