#include <bits/stdc++.h>
#define NM 100005
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
int n, m, cc;
vector<int> cp[NM];
vector<int> v[NM], in[NM];
vector<int> sf;
bitset<NM> viz;
void dfs1(int nod)
{
    viz[nod] = 1;
    for(auto it:v[nod])
        if(!viz[it])
            dfs1(it);
    sf.push_back(nod);
}
void dfs2(int nod)
{
    viz[nod] = 1;
    for(auto it:in[nod])
        if(!viz[it])
            dfs2(it);
    cp[cc].push_back(nod);
}
void read();
int main()
{
    read();
    for(int i=1; i<=n; i++)
        if(!viz[i])
            dfs1(i);
    viz.reset();
    for(int i=n-1; i>=0; i--)
        if(!viz[sf[i]])
        {
            ++cc;
            dfs2(sf[i]);
        }
    fout << cc << '\n';
    for(int i=1; i<=cc; i++)
    {
        sort(cp[i].begin(), cp[i].end());
        for(auto it:cp[i])
            fout << it << ' ';
        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);
        in[y].push_back(x);
    }
}