#include <bits/stdc++.h>
#define NM 100005
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
void read();
int n, m, nr;
vector<int> t, cc;
vector<int> v[NM], inv[NM];
bitset<NM> viz;
void dfs(int nod)
{
    viz[nod] = 1;
    for(auto it : v[nod])
        if(!viz[it])
            dfs(it);
    t.push_back(nod);
}
void kosaraju(int nod)
{
    cc.push_back(nod);
    viz[nod] = 1;
    for(auto it : inv[nod])
        if(!viz[it])
            kosaraju(it);
}
int main()
{
    read();
    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs(i);
    viz.reset();
    for(vector<int>::reverse_iterator it=t.rbegin(); it!=t.rend(); ++it)
        if(!viz[*it])
        {
            ++nr;
            kosaraju(*it);
        }
    fout << nr << '\n';
    viz.reset();
    for(vector<int>::reverse_iterator it=t.rbegin(); it!=t.rend(); ++it)
        if(!viz[*it])
        {
            cc.clear();
            kosaraju(*it);
            sort(cc.begin(), cc.end());
            for(auto afisare : cc)
                fout << afisare << ' ';
            fout << '\n';
        }

    return 0;
}
void read()
{
    fin >> n >> m;
    for(int i=1; i<=m; i++)
    {
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }
}