#include <bits/stdc++.h>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int nmax = 1e5+3;
void dfs(int nod);
void invdfs(int nod);

int n, m, nrcomp, comp[nmax];
bool viz[nmax];
vector<int> adj[nmax], invadj[nmax], c[nmax], topsort;

int main()
{
    fin>>n>>m;
    for(int i = 1; i <= m; ++i)
    {
        int x, y;
        fin>>x>>y;
        adj[x].push_back(y);
        invadj[y].push_back(x);
    }

    for(int i = 1; i <= n; ++i)
    {
        if(!viz[i])
            dfs(i);
    }
    reverse(topsort.begin(), topsort.end());

    for(int i = 0; i < n; ++i)
    {
        if(!comp[topsort[i]])
        {
            ++nrcomp;
            invdfs(topsort[i]);
        }
    }
    fout<<nrcomp<<"\n";
    for(int i = 1; i <= nrcomp; ++i)
    {
        for(auto nod : c[i])
            fout<<nod<<" ";
        fout<<"\n";
    }
    return 0;
}
void invdfs(int nod)
{
    comp[nod] = nrcomp;
    c[nrcomp].push_back(nod);
    for(auto i : invadj[nod])
    {
        if(!comp[i])
            invdfs(i);
    }
}

void dfs(int nod)
{
    viz[nod] = 1;
    for(auto i : adj[nod])
    {
        if(!viz[i])
            dfs(i);
    }
    topsort.push_back(nod);
}