#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>

using namespace std;

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

const int NMax = 100000;

vector <int> g[NMax + 5], gt[NMax + 5], sol[NMax + 5];
int n, m, nr, code;
int top[NMax + 5];
bool use[NMax + 5];

void Read(){
    fin >> n >> m;
    for (int i = 1; i <= m; i++){
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
}

void TopSort(int node){
    use[node] = 1;
    for (auto other : g[node])
        if (!use[other])
            TopSort(other);
    top[++nr] = node;
}

void DFS(int node, int code){
    use[node] = 1;
    sol[code].push_back(node);
    for (auto other : gt[node])
        if (!use[other])
            DFS(other, code);
}

void Solve(){
    for (int i = 1; i <= n; i++)
        if (!use[i])
            TopSort(i);
    memset(use, 0, sizeof use);
    for (int i = nr; i >= 1; i--)
        if (!use[top[i]]){
            ++code;
            DFS(top[i], code);
        }
}

void Print(){
    fout << code << '\n';
    for (int i = 1; i <= code; i++){
        for (auto node : sol[i])
            fout << node << ' ';
        fout << '\n';
    }
}

int main(){
    Read();
    Solve();
    Print();
    return 0;
}