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

using namespace std;

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

const int dim = 1e5 + 5;

int n, m;
vector<int> vec[dim], componente[dim];
vector<int> vecT[dim];
bool viz[dim];

stack<int> st;

void clearViz() {
    for (int i=0; i<dim; i++) viz[i] = 0;
}

void DFS(int nod) {
    viz[nod] = 1;

    for (auto y:vec[nod]) {
        if (!viz[y]) {
            DFS(y);
        }
    }
    st.push(nod);
}

void DFS2(int nod, int cnt) {
    viz[nod] = 1;
    componente[cnt].push_back(nod);
    for (auto y:vecT[nod]) {
        if (!viz[y]) {
            DFS2(y, cnt);
        }
    }
}

int main() {
    in >> n >> m;

    int x, y;

    for (int i=0; i<m; i++) {
        in >> x >> y;
        vec[x].push_back(y);
        vecT[y].push_back(x);
    }

    for (int i=1; i<=n; i++) {
        if (!viz[i]) DFS(i);
    }

    clearViz();

    int cnt = 0;
    while (!st.empty()) {
        int x = st.top();
        st.pop();

        if (!viz[x]) {
            cnt++;
            DFS2(x, cnt);
        }
    }

    out << cnt << "\n";
    for (int i=1; i<=cnt; i++) {
        for (auto y:componente[i]) {
            out << y << " ";
        }
        out << "\n";
    }

    return 0;
}