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

using namespace std;

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

vector <int> v[100001], vt[100001], sol[100001];
int s, n, m, color[100001], c;
stack <int> stash;

void citire () {
    fin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
}
/// if there is any edge other than "tree", then the graph has at least a cycle
void dfs (int nod) {
    color[nod] = 1;
    int size = v[nod].size();
    for (int i = 0; i < size; ++i) {
        int y = v[nod][i];
        if (color[y] == 0) {
            //fout << nod << " " << y << " " << "tree" << '\n';
            dfs(y);
        }
    }
    color[nod] = 2;
    stash.push(nod);
}

void color_index () {
    for (int i = 1; i <= n; ++i) {
        color[i] = 0;
    }
}

void dfst (int nod) {
    sol[c].push_back(nod);
    color[nod] = 1;
    int size = vt[nod].size();
    for (int i = 0; i < size; ++i) {
        int y = vt[nod][i];
        if (color[y] == 0) {
            //fout << nod << " " << y << " " << "tree" << '\n';
            dfst(y);
        }
    }
    color[nod] = 2;
}

int main () {
    citire();
    for (int i = 1; i <= n; ++i) {
        if (color[i] == 0) {
            dfs(i);
        }
    }
    color_index();
    while (not stash.empty()) {
        if (color[stash.top()] == 0) {
            c++;
            dfst(stash.top());
        }
        stash.pop();
    }
    fout << c;
    fout << '\n';
    for (int i = 1; i <= c; ++i) {
        int size = sol[i].size();
        for (int j = 0; j < size; ++j) {
            fout << sol[i][j] << " ";
        }
        fout << '\n';
    }
}