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

const int maxim = 100002;
int n, m, pluss[maxim], minuss[maxim], componente[maxim], nrComp = 0;
vector<int> a[maxim], transpus[maxim];

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

void citireOrientat(){
    int x, y;
    in >> n >> m;
    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){
    pluss[x] = 1;
    for(auto j: a[x])
        if(pluss[j] == 0)
            dfs(j);
}

void dfsTranspus(int x){
    minuss[x] = 1;
    for(auto j: transpus[x])
        if(minuss[j] == 0)
            dfsTranspus(j);
}

int main(){
    citireOrientat();
    for(int i = 1; i <= n; i++){
        if(componente[i] == 0){
            for(int j = 1; j <= n; j++)
                minuss[j] = pluss[j] = 0;
            dfs(i);
            dfsTranspus(i);
            nrComp++;
            for(int x = 1; x <= n; x++)
                if(minuss[x] == 1 && pluss[x] == 1)
                    componente[x] = nrComp;
        }
    }
    out << nrComp << "\n";
    for(int i = 1; i <= nrComp; i++){
        for(int j = 1; j <= n; j++)
            if(componente[j] == i)
                out << j << " ";
        out << "\n";
    }
    return 0;
}