#include <iostream>
#include <vector>
#include <queue>
#include <fstream>
#include <bitset>
#include <algorithm>

using namespace std;

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

const int N = 100000; 

vector< vector<int> >succ;
vector< vector<int> >pred;
vector< vector<int> >ctc;
vector<int>sort_top;
bitset<N + 1> viz;

void dfs(int x){
    viz[x] = 1;
    for(auto y : succ[x]){
        if(!viz[y]){
            dfs(y);
        }
    }
    sort_top.push_back(x);
}
void dfst(int x, vector<int>&v){
    viz[x] = 1;
    v.push_back(x);
    for(int i : pred[x]){
        if(!viz[i]){
            dfst(i, v);
        }
    }
}

int main(){
    int n, m;
    in >> n >> m;
    succ.resize(n + 1);
    pred.resize(n + 1);
    for(int i = 1; i <= m; i++){
        int x, y;
        in >> x >> y;
        succ[x].push_back(y);
        pred[y].push_back(x);
    }
    viz.reset();
    for(int i = 1; i <= n; i++){
        if(!viz[i]){
            dfs(i);
        }
    }
    reverse(sort_top.begin(), sort_top.end());
    viz.reset();
    for(int i : sort_top){
        if(!viz[i]){
            vector<int>v;
            dfst(i, v);
            ctc.push_back(v);
        }
    }
    out << ctc.size() << '\n';
    for(auto i : ctc){
        for(auto j : i){
            out << j << " ";
        }
        out << '\n';
    }
    in.close();
    out.close();
    return 0;
}