#include <bits/stdc++.h>

using namespace std;
int visited[100001];
vector<vector<int>>adj;
vector<vector<int>>ans;
vector<vector<int>>adj_rev;
void dfs(int x,vector<int>&auxv, vector<vector<int>>&adjaux)
{
    visited[x]=1;

    for(int i = 0; i < adjaux[x].size(); i++)
    {
        if(!visited[adjaux[x][i]])
        dfs(adjaux[x][i],auxv,adjaux);
    }
    auxv.push_back(x);
}

int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
    int n,m;
    cin>>n>>m;
    adj.resize(n+1,{});
    adj_rev.resize(n+1,{});
    for(int i = 0; i < m; i++)
    {
        int a,b;
        cin>>a>>b;
        adj[a].push_back(b);
    }
    vector<int>ordine;
    for(int i = 1; i <= n; i++)
    {
        if(!visited[i])
        {
            dfs(i,ordine,adj);
        }
    }
    for(int i = 1; i <= n; i++)
    {
        for(int j = 0; j < adj[i].size(); j++)
        {
            adj_rev[adj[i][j]].push_back(i);
        }
        visited[i] = 0;
    }
    for(int i = ordine.size()-1; i >= 0; i--)
    {
        if(!visited[ordine[i]])
        {
            vector<int>componenta;
            dfs(ordine[i],componenta,adj_rev);
            sort(componenta.begin(),componenta.end());
            ans.push_back(componenta);
        }
    }
    cout<<(int)(ans.size())<<'\n';
    for(int i = 0; i < ans.size(); i++)
    {
        for(int j = 0; j < ans[i].size(); j++)
        {
            cout<<ans[i][j]<<" ";
        }
        cout<<'\n';
    }
    return 0;
}