#include <bits/stdc++.h>
using namespace std;

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

vector<vector<int>> grph  = vector<vector<int>>(100001);
vector<vector<int>> grph2  = vector<vector<int>>(100001);
vector<bool> viz = vector<bool>(100001, false);
queue<int> pri;
int cnt = 0;
vector<vector<int>>ctc = vector<vector<int>>(100001);



void dfs1(int x){
    viz[x] = true;

    pri.push(x);
    for (const auto &item: grph[x]) {
        if(!viz[item]){
            dfs1(item);
        }

    }
}

void dfs2(int x){
    viz[x] = true;
    ctc[cnt].push_back(x);

    for (const auto &item: grph2[x]) {
        if(viz[item] ==false){
            dfs2(item);
        }
    }

}

int main() {
    int n, m;

    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y;
        fin >> x >> y;
        grph[x].push_back(y);
        grph2[y].push_back(x);
    }


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

    viz = vector<bool>(100001, false);

    while (!pri.empty()) {
        int k = pri.front();
        if (viz[k] == false) {
            cnt++;
            dfs2(k);
        }
        pri.pop();

    }
    fout<<cnt;
    for(int i=1;i<=cnt;i++){
        fout<<endl;
        for (const auto &item: ctc[i]) {
            fout<<item<<" ";
        }
    }
};