#include <bits/stdc++.h>

using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int nmax = 1e5+2;
void dfs1(int nod);
void dfs2(int nod);

int n, m, nrctc;
bool viz[nmax], viz2[nmax];
vector<int> adj[nmax], invadj[nmax], ctc[nmax];
stack<int> s;

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])
            dfs1(i);
    }
    while(!s.empty())
    {
        if(!viz2[s.top()])
        {
            ++nrctc;
            dfs2(s.top());
        }
        s.pop();
    }
    fout<<nrctc<<"\n";
    for(int i = 1; i <= nrctc; ++i)
    {
        for(auto nod : ctc[i])
            fout<<nod<<" ";
        fout<<"\n";
    }


    return 0;
}

void dfs2(int nod)
{
    viz2[nod] = true;
    ctc[nrctc].push_back(nod);
    for(auto i : invadj[nod])
    {
        if(!viz2[i])
            dfs2(i);
    }
}

void dfs1(int nod)
{
    viz[nod] = true;
    for(auto i : adj[nod])
    {
        if(!viz[i])
            dfs1(i);
    }
    s.push(nod);
}