#include <iostream>
#include <vector>
#include <utility>
#include <fstream>

using namespace std;

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

int n, m;
vector<int> a[100001], b[100001];
int v1[100001], v2[100001], ST[100001];

void citire() {
    for(int i = 0; i < m; i++) {
        int x, y;
        in >> x >> y;

        a[x].push_back(y);
        b[y].push_back(x);
    }
}

int nr = 1;
void dfs1(int k) {
    v1[k] = 1;

    for(int l: a[k]) {
        if(v1[l] == 0) {
            dfs1(l);
        }
    }
    ST[nr] = k;
    nr++;
}

void dfs2(int k, int cmp) {
    v2[k] = cmp;

    for(int l: b[k]) {
        if(v2[l] == 0) {
            dfs2(l, cmp);
        }
    }

    //cout << k << " ";
}

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

    for(int i = 1; i <= n; i++) {
        if(v1[i] == 0) {
            dfs1(i);
        }
    }

    int cmp = 1;
    for(int i = n; i >= 1; i--) {
        if(v2[ST[i]] == 0) {
            dfs2(ST[i], cmp);
            cmp++;
        }
    }

    out << --cmp << "\n";

    for(int i = 1; i <= cmp; i++) {
        for(int j = 1; j <= n; j++) {
            if(v2[j] == i) {
                out << j << " ";
            }
        }
        out << "\n";
    }

    in.close();
    out.close();

    return 0;
}