#include <bits/stdc++.h>
#define N 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
stack < int > S;
vector<int> g[N],gt[N],ctc[N];
int n, m, nctc;
int v[N];
void Read()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int x,y;
        fin >> x >> y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
}
void dfs(int nod)
{
    v[nod] = 1;
    for(unsigned int i=0; i<g[nod].size();i++) {
        int vecin = g[nod][i];
        if(!v[vecin])
            dfs(vecin);
    }
    S.push(nod);
}
void dfst(int nod)
{
    v[nod] = 2;
    ctc[nctc].push_back(nod);
    for(unsigned int i=0; i<gt[nod].size();i++) {
        int vecin = gt[nod][i];
        if(v[vecin]==1)
            dfst(vecin);
    }
}
void Solve()
{
    for(int i=1;i<=n;i++)
        if(!v[i])
            dfs(i);
    while(!S.empty()) {
        int nod = S.top();
        S.pop();
        //cout << nod << " ";
        if (v[nod] == 1) {
            nctc++;
            dfst(nod);
        }
    }
}
void Bbs()
{
   for(int i=1; i<=nctc; i++)
   {
     sort(ctc[i].begin(), ctc[i].end());
   }
}
void Print()
{
    fout << nctc << endl;
    for(int i = 1; i <= nctc; i++) {
        for(unsigned int j = 0; j < ctc[i].size(); j++)
            fout << ctc[i][j] <<" ";
        fout<<"\n";
    }
}
int main()
{
    Read();
    Solve();
    Bbs();
    Print();
    return 0;
}