#include <bits/stdc++.h>

using namespace std;
const int lim = 1e5;
int diri[4] = {-1, 0, 1, 0}, dirj[4] = {0, 1, 0, -1};
vector <int> ad[lim + 1], adt[lim + 1], srt, aux;
vector <vector<int>> ctc;
bool viz[lim + 1];

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

void dfs(int nod){
    viz[nod] = true;
    for(auto fiu : ad[nod])
        if(!viz[fiu])
            dfs(fiu);
    srt.push_back(nod);
}

void dfsi(int nod){
    viz[nod] = true;
    aux.push_back(nod);
    for(auto fiu : adt[nod])
        if(!viz[fiu])
            dfsi(fiu);
}

int main()
{
    int n, m, x, y;
    fin >> n >> m;
    for(int i = 0; i < m; i++){
        fin >> x >> y;
        ad[x].push_back(y);
        adt[y].push_back(x);
    }
    for(int i = 1; i <= n; i++)
        if(!viz[i])
            dfs(i);
    reverse(srt.begin(), srt.end());
    memset(viz, 0, lim + 1);
    for(auto e : srt)
        if(!viz[e]){
            aux.clear();
            dfsi(e);
            ctc.push_back(aux);
        }
    fout << ctc.size() << '\n';
    for(auto v : ctc){
        for(auto e : v)
            fout << e << ' ';
        fout << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}