#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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

vector<int> GM[100005], GTM[100005], comp[100005];
bool viz[100005];
int postordine[100005], nr, cnt;

void DFS(int nod)
{
    viz[nod] = 1;
    for(int i = 0; i < GM[nod].size(); ++i)
        if(!viz[GM[nod][i]])
            DFS(GM[nod][i]);
    postordine[++nr] = nod;
}

void DFST(int nod){
    comp[cnt].push_back(nod);
    viz[nod] = 0;
    for(int i = 0; i < GTM[nod].size(); ++i)
        if(viz[GTM[nod][i]])
            DFST(GTM[nod][i]);
}

int main()
{
    ios_base::sync_with_stdio(false);
    int n, m;
    fin >> n >> m;

    for(int i = 1; i <= m; ++i)
    {
        int x, y;
        fin >> x >> y;

        GM[x].push_back(y);
        GTM[y].push_back(x);
    }

    for(int i = 1; i <= n; ++i)
        if(!viz[i])
            DFS(i);

    for(int i = n; i >= 1; --i)
        if(viz[postordine[i]])
        {
            ++cnt;
            DFST(postordine[i]);
        }
    fout << cnt << '\n';
    for(int i = 1; i <= cnt; ++i){
        sort(comp[i].begin(), comp[i].end());
        for(int j = 0; j < comp[i].size(); ++j)
            fout << comp[i][j] << ' ';
        fout << '\n';
    }
    return 0;
}