#include <bits/stdc++.h>

using namespace std;

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

int n, m;
vector<bool> viz;

void dfs(int nod, vector<vector<int>> &edges, vector<int> &add_to)
{
    viz[nod] = true;
    for(auto i : edges[nod])
        if(!viz[i])
            dfs(i, edges, add_to);
    add_to.push_back(nod);
}

int main()
{
    fin >> n >> m;
    vector<vector<int>> rev_edges(n), edges(n);
    vector<int> st;
    viz.resize(n);
    for(int i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        x--;
        y--;
        edges[x].push_back(y);
        rev_edges[y].push_back(x);
    }
    for(int nod = 0; nod < n; nod++)
    {
        if(!viz[nod])
            dfs(nod, edges, st);
    }
    viz.clear();
    viz.resize(n);
    vector<vector<int>> ctc;
    for(int i = st.size()-1; i >= 0; i--)
        if(viz[st[i]] == 0)
        {
            ctc.push_back(vector<int>());
            dfs(st[i], rev_edges, ctc.back());
        }
    fout << ctc.size() << "\n";
    for(auto cm : ctc)
    {
        for(auto nod : cm)
            fout << nod+1 << " ";
        fout << "\n";
    }
    return 0;
}