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

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

int N, M;
vector<vector<int>> G, CC;
vector<int> Index, L, C;
vector<bool> Instack;
stack<int> Stk;
int idx, nrc;

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

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

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

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 (L[nod] == Index[nod]) {
        nrc++;
        C.clear();
        int nod2;
        do {
            nod2 = Stk.top(); Stk.pop();
            C.push_back(nod2);
            Instack[nod2] = false;
        } while (nod2 != nod);
        CC.push_back(C);
    }
}

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);
    }
}