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

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

int N, M;
vector<vector<int>> G1, G2, CC;
vector<int> C;
vector<bool> s, s1;
stack<int> S;
int nrc;

void Read();
void DF(int x);
void DFt(int x);
void Write();

int main() {
    Read();
    for (int i = 1; i <= N; i++)
        if (!s[i]) DF(i);
    int x;
    while (!S.empty()) {
        x = S.top(); S.pop();
        if (!s1[x]) {
            nrc++;
            C.clear();
            DFt(x);
            CC.push_back(C);
        }
    }
    Write();
    fin.close();
    fout.close();
    return 0;
}

void DFt(int x) {
    s1[x] = true;
    C.push_back(x);
    for (const auto & e : G2[x]) {
        if (!s1[e]) DFt(e);
    }
}

void DF(int x) {
    s[x] = true;
    for (const auto e : G1[x])
        if (!s[e]) DF(e);
    S.push(x);
}

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

void Read() {
    fin >> N >> M;
    G1 = G2 = vector<vector<int>>(N + 1);
    s = s1 = vector<bool>(N + 1, false);
    for (int i = 1, x, y; i <= M; i++) {
        fin >> x >> y;
        G1[x].push_back(y);
        G2[y].push_back(x);
    }
}