#include <bits/stdc++.h>
using namespace std;
vector<vector<int>>adj(5000);
vector<vector<int>>tadj(5000);
bool vis[5000];
int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    vector<vector<int>>ans;
    int n,m;
    cin >> n >> m;
    for(int i=0;i<m;i++){
        int a,b;
        cin >> a >> b;
        a--;
        b--;
        adj[a].push_back(b);
        tadj[b].push_back(a);
    }
    queue<int>pq;
    queue<int>od;
    for(int i = 0;i<n;i++){
        if(!vis[i]){
            vis[i] = 1;
            pq.push(i);
            while(pq.size()){
                int nod = pq.front();
                pq.pop();
                od.push(nod);
                for(auto v : adj[nod]){
                    if(!vis[v]) {
                        vis[v] = 1;
                        pq.push(v);
                    }
                    
                }
            }
        }
    }
    
    while(od.size()){
        int nod = od.front();
        od.pop();
        if(vis[nod]){
            vector<int>tmp;
            vis[nod] = 0;
            pq.push(nod);
            while(pq.size()){
                int c = pq.front();
                tmp.push_back(c);
                pq.pop();
                for(auto v : tadj[c]){
                    if(vis[v]){
                        vis[v] = 0;
                        pq.push(v);
                    }
                }
            }
            ans.push_back(tmp);
        }
        
    }
    cout<<ans.size()<<"\n";
    for(auto v : ans){
        for(auto e : v) cout<<e+1<<" ";
        cout<<"\n";
    }

    

    return 0;
}