#include<iostream>
#include<fstream>
#include<vector>
#include<stack>
using namespace std;

const int maxim = 100002;
int n, m, vizitate[maxim], contor = 0;
vector<int> a[maxim], transpus[maxim], solutie[maxim];
stack<int> s;

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

void citireOrientat(){
    in >> n >> m;
    int x, y;
    for(int i = 1; i <= m; i++){
        in >> x >> y;
        a[x].push_back(y);
        transpus[y].push_back(x); //formez graful transpus
    }
}

void dfs(int x){
    vizitate[x] = 1;
    for(auto j: a[x])
        if(vizitate[j] == 0)
            dfs(j);
    s.push(x);
}

void dfsTranspus(int x){
    vizitate[x] = 2;
    solutie[contor].push_back(x);
    for(auto j: transpus[x])
        if(vizitate[j] == 1)
            dfsTranspus(j);
}


int main(){
    citireOrientat();
    for(int i = 1; i <= n; i++)
        if(vizitate[i] == 0)
            dfs(i);
    while(s.empty() != 1){
        int nod = s.top();
        if(vizitate[nod] == 1){
            contor++;
            dfsTranspus(nod);
        }
        s.pop();
    }
    out << contor << "\n";
    for(int i = 1;i <= contor; i++){
        for(auto j: solutie[i])
            out << j <<" ";
        out << "\n";
    }
    return 0;
}